[PATCH] Magic block for modules

This implements a proposal made last november:

http://archives.postgresql.org/pgsql-hackers/2005-11/msg00578.php

Basically, it tries to catch people loading modules which belong to the
wrong version or have had certain constants changed, or architechture
mismatches. It's a bit more fine grained though, it currently catches
changes in any of the following:

PG_VERSION_NUM
CATALOG_VERSION_NO
the size of 8 basic C types
BLCKSZ
NAMEDATALEN
HAVE_INT64_TIMESTAMP
INDEX_MAX_KEYS
FUNC_MAX_ARGS
VARHDRSZ
MAXDIM
The compiler used (only brand, not version)

It may be overkill, but better safe than sorry. The only one I'm
ambivalent about is the first one. We don't require a recompile between
minor version changes, or do we?

All it requires is to include the header "pgmagic.h" and to put
somewhere in their source:

PG_MODULE_MAGIC

Currently, modules without a magic block are merely logged at LOG
level. This needs some discussion though.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.