thd_charset copy in lex

sql/sql_lex.cc

@@ -165,6 +165,7 @@ LEX *lex_start(THD *thd, uchar *buf,uint length)
   lex->select_lex.ftfunc_list= &lex->select_lex.ftfunc_list_alloc;
   lex->current_select= &lex->select_lex;
   lex->convert_set= (lex->thd= thd)->variables.convert_set;
+  lex->thd_charset= lex->thd->variables.thd_charset;
   lex->yacc_yyss=lex->yacc_yyvs=0;
   lex->ignore_space=test(thd->sql_mode & MODE_IGNORE_SPACE);
   lex->slave_thd_opt=0;

sql/sql_lex.h

@@ -432,7 +432,7 @@ typedef struct st_lex
   create_field	      *last_field;
   Item *default_value, *comment;
   CONVERT *convert_set;
-  CONVERT *thd_convert_set;			// Set with SET CHAR SET
+  CHARSET_INFO *thd_charset;
   LEX_USER *grant_user;
   gptr yacc_yyss,yacc_yyvs;
   THD *thd;