Code cleanup to get fewer reallocs() during execution.

- Changed TABLE->alias to String to get fewer reallocs when alias are used.
- Preallocate some buffers

Changed some String->c_ptr() -> String->ptr() when \0 is not needed.
Fixed wrong usage of String->ptr() when we need a \0 terminated string.
Use my_strtod() instead of my_atof() to avoid having to add \0 to string.
c_ptr() -> c_ptr_safe() to avoid warnings from valgrind.
zr 

sql/event_db_repository.cc:
  Update usage of TABLE->alias
sql/event_scheduler.cc:
  c_ptr() -> c_ptr_safe()
sql/events.cc:
  c_ptr() -> ptr() as \0 was not needed
sql/field.cc:
  Update usage of TABLE->alias
sql/field.h:
  Update usage of TABLE->alias
sql/ha_partition.cc:
  Update usage of TABLE->alias
sql/handler.cc:
  Update usage of TABLE->alias
  Fixed wrong usage of str.ptr()
sql/item.cc:
  Fixed error where code wrongly assumed string was \0 terminated.
sql/item_func.cc:
  c_ptr() -> c_ptr_safe()
  Update usage of TABLE->alias
sql/item_sum.h:
  Use my_strtod() instead of my_atof() to avoid having to add \0 to string
sql/lock.cc:
  Update usage of TABLE->alias
sql/log.cc:
  c_ptr() -> ptr() as \0 was not needed
sql/log_event.cc:
  c_ptr_quick() -> ptr() as \0 was not needed
sql/opt_range.cc:
  ptr() -> c_ptr() as \0 is needed
sql/opt_subselect.cc:
  Update usage of TABLE->alias
sql/opt_table_elimination.cc:
  Update usage of TABLE->alias
sql/set_var.cc:
  ptr() -> c_ptr() as \0 is needed
  c_ptr() -> c_ptr_safe()
sql/sp.cc:
  c_ptr() -> ptr() as \0 was not needed
sql/sp_rcontext.cc:
  
  Update usage of TABLE->alias
sql/sql_base.cc:
  Preallocate buffers
  Update usage of TABLE->alias
sql/sql_class.cc:
  Fix arguments to sprintf() to work even if string is not \0 terminated
sql/sql_insert.cc:
  Update usage of TABLE->alias
  c_ptr() -> ptr() as \0 was not needed
sql/sql_load.cc:
  Preallocate buffers
  Trivial optimizations
sql/sql_parse.cc:
  Trivial optimization
sql/sql_plugin.cc:
  c_ptr() -> ptr() as \0 was not needed
sql/sql_select.cc:
  Update usage of TABLE->alias
sql/sql_show.cc:
  Update usage of TABLE->alias
sql/sql_string.h:
  Added move() function to move allocated memory from one object to another.
sql/sql_table.cc:
  Update usage of TABLE->alias
  c_ptr() -> c_ptr_safe()
sql/sql_test.cc:
  ptr() -> c_ptr_safe()
sql/sql_trigger.cc:
  Update usage of TABLE->alias
  c_ptr() -> c_ptr_safe()
sql/sql_update.cc:
  Update usage of TABLE->alias
sql/sql_view.cc:
  ptr() -> c_ptr_safe()
sql/sql_yacc.yy:
  ptr() -> c_ptr()
sql/table.cc:
  
  Update usage of TABLE->alias
sql/table.h:
  Changed TABLE->alias to String to get fewer reallocs when alias are used.
storage/federatedx/ha_federatedx.cc:
  Use c_ptr_safe() to ensure strings are \0 terminated.
storage/maria/ha_maria.cc:
  Update usage of TABLE->alias
storage/myisam/ha_myisam.cc:
  Update usage of TABLE->alias
storage/xtradb/row/row0sel.c:
  Ensure that null bits in record are properly reset.
  (Old code didn't work as row_search_for_mysql() can be called twice while reading fields from one row.

sql/sql_insert.cc

@@ -2074,6 +2074,7 @@ TABLE *Delayed_insert::get_local_table(THD* client_thd)
   TABLE *copy;
   TABLE_SHARE *share;
   uchar *bitmap;
+  char *copy_tmp;
   DBUG_ENTER("Delayed_insert::get_local_table");
 
   /* First request insert thread to get a lock */
@@ -2106,14 +2107,15 @@ TABLE *Delayed_insert::get_local_table(THD* client_thd)
     the other record buffers and alignment are unnecessary.
   */
   thd_proc_info(client_thd, "allocating local table");
-  copy= (TABLE*) client_thd->alloc(sizeof(*copy)+
-				   (share->fields+1)*sizeof(Field**)+
-				   share->reclength +
-                                   share->column_bitmap_size*3);
-  if (!copy)
+  copy_tmp= (char*) client_thd->alloc(sizeof(*copy)+
+                                      (share->fields+1)*sizeof(Field**)+
+                                      share->reclength +
+                                      share->column_bitmap_size*3);
+  if (!copy_tmp)
     goto error;
 
   /* Copy the TABLE object. */
+  copy= new (copy_tmp) TABLE;
   *copy= *table;
   /* We don't need to change the file handler here */
   /* Assign the pointers for the field pointers array and the record. */
@@ -3502,7 +3504,7 @@ int select_create::write_to_binlog(bool is_trans, int errcode)
       Avoid to use thd->binlog_query() twice, otherwise it will print the unsafe
       warning twice.
     */
-    Query_log_event ev(thd, query.c_ptr_safe(), query.length(), is_trans,
+    Query_log_event ev(thd, query.ptr(), query.length(), is_trans,
                        FALSE, errcode);
     return mysql_bin_log.write(&ev);
   }