proposal: use errcontext for custom exception too

Hello

There are small issue in PL/pgSQL and custom exceptions. Custom
exception doesn't set a CONTEXT field. I propose change this behave
for WARNING or EXCEPTION level. The goal is same behave for custom
exception and builtin exception and it can help to identify a RAISE
statement that is responsible to exception.

./pl_exec.c
*** ./pl_exec.c.orig 2011-11-24 17:29:08.000000000 +0100
--- ./pl_exec.c 2011-11-24 18:23:51.513136718 +0100
***************
*** 2827,2833 ****
/*
* Throw the error (may or may not come back)
*/
! estate->err_text = raise_skip_msg; /* suppress traceback of raise */

ereport(stmt->elog_level,
(err_code ? errcode(err_code) : 0,
--- 2827,2834 ----
/*
* Throw the error (may or may not come back)
*/
! if (stmt->elog_level < WARNING)
! estate->err_text = raise_skip_msg; /* suppress traceback of raise notice */

ereport(stmt->elog_level,
(err_code ? errcode(err_code) : 0,

Regards

Pavel Stehule