Prevent error recursion crashes when encoding conversion fails (Tom)

This change extends fixes made in the last two minor releases for related failure scenarios. The previous fixes were narrowly tailored for the original problem reports, but we have now recognized that any error thrown by an encoding conversion function could potentially lead to infinite recursion while trying to report the error. The solution therefore is to disable translation and encoding conversion and report the plain-ASCII form of any error message, if we find we have gotten into a recursive error reporting situation. (CVE-2009-0922)

Disallow CREATE CONVERSION with the wrong encodings for the specified conversion function (Heikki)

This prevents one possible scenario for encoding conversion failure. The previous change is a backstop to guard against other kinds of failures in the same area.

Fix core dump when to_char() is given format codes that are inappropriate for the type of the data argument (Tom)

Fix decompilation of CASE WHEN with an implicit coercion (Tom)

This mistake could lead to Assert failures in an Assert-enabled build, or an “unexpected CASE WHEN clause” error message in other cases, when trying to examine or dump a view.

Fix possible misassignment of the owner of a TOAST table's rowtype (Tom)

If CLUSTER or a rewriting variant of ALTER TABLE were executed by someone other than the table owner, the pg_type entry for the table's TOAST table would end up marked as owned by that someone. This caused no immediate problems, since the permissions on the TOAST rowtype aren't examined by any ordinary database operation. However, it could lead to unexpected failures if one later tried to drop the role that issued the command (in 8.1 or 8.2), or “owner of data type appears to be invalid” warnings from pg_dump after having done so (in 8.3).

Clean up PL/pgSQL error status variables fully at block exit (Ashesh Vashi and Dave Page)

This is not a problem for PL/pgSQL itself, but the omission could cause the PL/pgSQL Debugger to crash while examining the state of a function.

Add MUST (Mauritius Island Summer Time) to the default list of known timezone abbreviations (Xavier Bugaud)