Bug#33637 SHOW PROCEDURE CODE/SHOW FUNCTION CODE sp_name gives a syntax error.

Backport for 5.5

In non debug builds, the statements:
- SHOW PROCEDURE CODE
- SHOW FUNCTION CODE
used to fail with a "syntax error", which is misleading.

These statements have been changed to return the following error for non
debug builds:
ERROR HY000: The 'SHOW PROCEDURE|FUNCTION CODE' feature is disabled; you
need MySQL built with '--with-debug' to have it working

For debug builds (./configure --with-debug), nothing is changed.

sql/sql_parse.cc

@@ -4658,10 +4658,10 @@ create_sp_error:
       }
       break;
     }
-#ifndef DBUG_OFF
   case SQLCOM_SHOW_PROC_CODE:
   case SQLCOM_SHOW_FUNC_CODE:
     {
+#ifndef DBUG_OFF
       sp_head *sp;
 
       if (lex->sql_command == SQLCOM_SHOW_PROC_CODE)
@@ -4678,8 +4678,12 @@ create_sp_error:
         goto error;
       }
       break;
-    }
+#else
+      my_error(ER_FEATURE_DISABLED, MYF(0),
+               "SHOW PROCEDURE|FUNCTION CODE", "--with-debug");
+      goto error;
 #endif // ifndef DBUG_OFF
+    }
   case SQLCOM_SHOW_CREATE_TRIGGER:
     {
       if (lex->spname->m_name.length > NAME_LEN)