Reduce usage of strlen()

Changes:
- To detect automatic strlen() I removed the methods in String that
  uses 'const char *' without a length:
  - String::append(const char*)
  - Binary_string(const char *str)
  - String(const char *str, CHARSET_INFO *cs)
  - append_for_single_quote(const char *)
  All usage of append(const char*) is changed to either use
  String::append(char), String::append(const char*, size_t length) or
  String::append(LEX_CSTRING)
- Added STRING_WITH_LEN() around constant string arguments to
  String::append()
- Added overflow argument to escape_string_for_mysql() and
  escape_quotes_for_mysql() instead of returning (size_t) -1 on overflow.
  This was needed as most usage of the above functions never tested the
  result for -1 and would have given wrong results or crashes in case
  of overflows.
- Added Item_func_or_sum::func_name_cstring(), which returns LEX_CSTRING.
  Changed all Item_func::func_name()'s to func_name_cstring()'s.
  The old Item_func_or_sum::func_name() is now an inline function that
  returns func_name_cstring().str.
- Changed Item::mode_name() and Item::func_name_ext() to return
  LEX_CSTRING.
- Changed for some functions the name argument from const char * to
  to const LEX_CSTRING &:
  - Item::Item_func_fix_attributes()
  - Item::check_type_...()
  - Type_std_attributes::agg_item_collations()
  - Type_std_attributes::agg_item_set_converter()
  - Type_std_attributes::agg_arg_charsets...()
  - Type_handler_hybrid_field_type::aggregate_for_result()
  - Type_handler_geometry::check_type_geom_or_binary()
  - Type_handler::Item_func_or_sum_illegal_param()
  - Predicant_to_list_comparator::add_value_skip_null()
  - Predicant_to_list_comparator::add_value()
  - cmp_item_row::prepare_comparators()
  - cmp_item_row::aggregate_row_elements_for_comparison()
  - Cursor_ref::print_func()
- Removes String_space() as it was only used in one cases and that
  could be simplified to not use String_space(), thanks to the fixed
  my_vsnprintf().
- Added some const LEX_CSTRING's for common strings:
  - NULL_clex_str, DATA_clex_str, INDEX_clex_str.
- Changed primary_key_name to a LEX_CSTRING
- Renamed String::set_quick() to String::set_buffer_if_not_allocated() to
  clarify what the function really does.
- Rename of protocol function:
  bool store(const char *from, CHARSET_INFO *cs) to
  bool store_string_or_null(const char *from, CHARSET_INFO *cs).
  This was done to both clarify the difference between this 'store' function
  and also to make it easier to find unoptimal usage of store() calls.
- Added Protocol::store(const LEX_CSTRING*, CHARSET_INFO*)
- Changed some 'const char*' arrays to instead be of type LEX_CSTRING.
- class Item_func_units now used LEX_CSTRING for name.

Other things:
- Fixed a bug in mysql.cc:construct_prompt() where a wrong escape character
  in the prompt would cause some part of the prompt to be duplicated.
- Fixed a lot of instances where the length of the argument to
  append is known or easily obtain but was not used.
- Removed some not needed 'virtual' definition for functions that was
  inherited from the parent. I added override to these.
- Fixed Ordered_key::print() to preallocate needed buffer. Old code could
  case memory overruns.
- Simplified some loops when adding char * to a String with delimiters.

sql/sql_select.cc

@@ -804,7 +804,7 @@ void vers_select_conds_t::print(String *str, enum_query_type query_type) const
     DBUG_ASSERT(0);
     break;
   case SYSTEM_TIME_ALL:
-    str->append(" FOR SYSTEM_TIME ALL");
+    str->append(STRING_WITH_LEN(" FOR SYSTEM_TIME ALL"));
     break;
   }
 }
@@ -13477,8 +13477,11 @@ make_join_readinfo(JOIN *join, ulonglong options, uint no_jbuf_after)
                  char buff[256];
                  String str(buff,sizeof(buff),system_charset_info);
                  str.length(0);
-                 str.append(tab->table? tab->table->alias.c_ptr() :"<no_table_name>");
-                 str.append(" final_pushdown_cond");
+                 if (tab->table)
+                   str.append(tab->table->alias);
+                 else
+                   str.append(STRING_WITH_LEN("<no_table_name>"));
+                 str.append(STRING_WITH_LEN(" final_pushdown_cond"));
                  print_where(tab->select_cond, str.c_ptr_safe(), QT_ORDINARY););
   }
   uint n_top_tables= (uint)(join->join_tab_ranges.head()->end -  
@@ -27733,13 +27736,13 @@ Index_hint::print(THD *thd, String *str)
     case INDEX_HINT_USE:    str->append(STRING_WITH_LEN("USE INDEX")); break;
     case INDEX_HINT_FORCE:  str->append(STRING_WITH_LEN("FORCE INDEX")); break;
   }
-  str->append (STRING_WITH_LEN(" ("));
+  str->append(STRING_WITH_LEN(" ("));
   if (key_name.length)
   {
     if (thd && !system_charset_info->strnncoll(
                              (const uchar *)key_name.str, key_name.length, 
-                             (const uchar *)primary_key_name, 
-                             strlen(primary_key_name)))
+                             (const uchar *)primary_key_name.str,
+                             primary_key_name.length))
       str->append(primary_key_name);
     else
       append_identifier(thd, str, &key_name);
@@ -27897,8 +27900,8 @@ void TABLE_LIST::print(THD *thd, table_map eliminated_tables, String *str,
 
       while ((hint= it++))
       {
-        str->append (STRING_WITH_LEN(" "));
-        hint->print (thd, str);
+        str->append(' ');
+        hint->print(thd, str);
       }
     }
   }
@@ -27920,21 +27923,21 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
       thd->lex->all_selects_list->link_next &&
       select_number != FAKE_SELECT_LEX_ID)
   {
-    str->append("/* select#");
+    str->append(STRING_WITH_LEN("/* select#"));
     str->append_ulonglong(select_number);
     if (thd->lex->describe & DESCRIBE_EXTENDED2)
     {
-      str->append("/");
+      str->append('/');
       str->append_ulonglong(nest_level);
 
       if (master_unit()->fake_select_lex &&
           master_unit()->first_select() == this)
       {
-        str->append(" Filter Select: ");
+        str->append(STRING_WITH_LEN(" Filter Select: "));
         master_unit()->fake_select_lex->print(thd, str, query_type);
       }
     }
-    str->append(" */ ");
+    str->append(STRING_WITH_LEN(" */ "));
   }
 
   str->append(STRING_WITH_LEN("select "));
@@ -28034,7 +28037,7 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
     if (cur_where)
       cur_where->print(str, query_type);
     else
-      str->append(cond_value != Item::COND_FALSE ? "1" : "0");
+      str->append(cond_value != Item::COND_FALSE ? '1' : '0');
   }
 
   // group by & olap
@@ -28066,7 +28069,7 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
     if (cur_having)
       cur_having->print(str, query_type);
     else
-      str->append(having_value != Item::COND_FALSE ? "1" : "0");
+      str->append(having_value != Item::COND_FALSE ? '1' : '0');
   }
 
   if (order_list.elements)
@@ -28080,12 +28083,11 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
 
   // lock type
   if (select_lock == select_lock_type::IN_SHARE_MODE)
-    str->append(" lock in share mode");
+    str->append(STRING_WITH_LEN(" lock in share mode"));
   else if (select_lock == select_lock_type::FOR_UPDATE)
-    str->append(" for update");
-
+    str->append(STRING_WITH_LEN(" for update"));
   if (unlikely(skip_locked))
-    str->append(" skip locked");
+    str->append(STRING_WITH_LEN(" skip locked"));
 
   // PROCEDURE unsupported here
 }