Changing field::field_name and Item::name to LEX_CSTRING

Benefits of this patch:
- Removed a lot of calls to strlen(), especially for field_string
- Strings generated by parser are now const strings, less chance of
  accidently changing a string
- Removed a lot of calls with LEX_STRING as parameter (changed to pointer)
- More uniform code
- Item::name_length was not kept up to date. Now fixed
- Several bugs found and fixed (Access to null pointers,
  access of freed memory, wrong arguments to printf like functions)
- Removed a lot of casts from (const char*) to (char*)

Changes:
- This caused some ABI changes
  - lex_string_set now uses LEX_CSTRING
  - Some fucntions are now taking const char* instead of char*
- Create_field::change and after changed to LEX_CSTRING
- handler::connect_string, comment and engine_name() changed to LEX_CSTRING
- Checked printf() related calls to find bugs. Found and fixed several
  errors in old code.
- A lot of changes from LEX_STRING to LEX_CSTRING, especially related to
  parsing and events.
- Some changes from LEX_STRING and LEX_STRING & to LEX_CSTRING*
- Some changes for char* to const char*
- Added printf argument checking for my_snprintf()
- Introduced null_clex_str, star_clex_string, temp_lex_str to simplify
  code
- Added item_empty_name and item_used_name to be able to distingush between
  items that was given an empty name and items that was not given a name
  This is used in sql_yacc.yy to know when to give an item a name.
- select table_name."*' is not anymore same as table_name.*
- removed not used function Item::rename()
- Added comparision of item->name_length before some calls to
  my_strcasecmp() to speed up comparison
- Moved Item_sp_variable::make_field() from item.h to item.cc
- Some minimal code changes to avoid copying to const char *
- Fixed wrong error message in wsrep_mysql_parse()
- Fixed wrong code in find_field_in_natural_join() where real_item() was
  set when it shouldn't
- ER_ERROR_ON_RENAME was used with extra arguments.
- Removed some (wrong) ER_OUTOFMEMORY, as alloc_root will already
  give the error.

TODO:
- Check possible unsafe casts in plugin/auth_examples/qa_auth_interface.c
- Change code to not modify LEX_CSTRING for database name
  (as part of lower_case_table_names)

sql/sql_repl.cc

@@ -865,7 +865,6 @@ get_binlog_list(MEM_ROOT *memroot)
         !(e->name= strmake_root(memroot, fname, length)))
     {
       mysql_bin_log.unlock_index();
-      my_error(ER_OUTOFMEMORY, MYF(0), length + 1 + sizeof(*e));
       DBUG_RETURN(NULL);
     }
     e->next= current_list;
@@ -3045,7 +3044,7 @@ int start_slave(THD* thd , Master_info* mi,  bool net_report)
   {
     /* connection was deleted while we waited for lock_slave_threads */
     mi->unlock_slave_threads();
-    my_error(WARN_NO_MASTER_INFO, mi->connection_name.length,
+    my_error(WARN_NO_MASTER_INFO, MYF(0), (int) mi->connection_name.length,
              mi->connection_name.str);
     DBUG_RETURN(-1);
   }
@@ -3303,7 +3302,7 @@ int reset_slave(THD *thd, Master_info* mi)
   {
     /* connection was deleted while we waited for lock_slave_threads */
     mi->unlock_slave_threads();
-    my_error(WARN_NO_MASTER_INFO, mi->connection_name.length,
+    my_error(WARN_NO_MASTER_INFO, MYF(0), (int) mi->connection_name.length,
              mi->connection_name.str);
     DBUG_RETURN(-1);
   }
@@ -3445,7 +3444,7 @@ static bool get_string_parameter(char *to, const char *from, size_t length,
     uint from_numchars= cs->cset->numchars(cs, from, from + from_length);
     if (from_numchars > length / cs->mbmaxlen)
     {
-      my_error(ER_WRONG_STRING_LENGTH, MYF(0), from, name, length / cs->mbmaxlen);
+      my_error(ER_WRONG_STRING_LENGTH, MYF(0), from, name, (int) (length / cs->mbmaxlen));
       return 1;
     }
     memcpy(to, from, from_length+1);
@@ -3514,7 +3513,7 @@ bool change_master(THD* thd, Master_info* mi, bool *master_info_added)
   {
     /* connection was deleted while we waited for lock_slave_threads */
     mi->unlock_slave_threads();
-    my_error(WARN_NO_MASTER_INFO, mi->connection_name.length,
+    my_error(WARN_NO_MASTER_INFO, MYF(0), (int) mi->connection_name.length,
              mi->connection_name.str);
     DBUG_RETURN(TRUE);
   }