Fix a failure of lowercase_tables2 test on powermacg5, introduced

by the patch for Bug#4968


sql/sql_parse.cc:
  Fix lowercase_tables2 test failure on powermacg5: table_case_name()
  function needed create_info.alias if lowercase_table_names=2, which
  was not set for the stack copy of HA_CREATE_INFO. Move the
  update of create_info.alias from create_table_precheck to 
  mysql_execute_command, so that it is done on the right object.

sql/sql_parse.cc

@@ -2500,6 +2500,7 @@ mysql_execute_command(THD *thd)
     if ((res= create_table_precheck(thd, tables, create_table)))
       goto unsent_create_error;
 
+    create_info.alias= create_table->alias;
 #ifndef HAVE_READLINK
     create_info.data_file_name= create_info.index_file_name= NULL;
 #else
@@ -5800,7 +5801,6 @@ int create_table_precheck(THD *thd, TABLE_LIST *tables,
 
   want_priv= ((lex->create_info.options & HA_LEX_CREATE_TMP_TABLE) ?
               CREATE_TMP_ACL : CREATE_ACL);
-  lex->create_info.alias= create_table->alias;
   if (check_access(thd, want_priv, create_table->db,
 		   &create_table->grant.privilege, 0, 0) ||
       check_merge_table_access(thd, create_table->db,