locale issues on win32 (fix?)

Hello!

Here is a temp fix for the locale issues on win32. It passes regression
tests, but is *NOT* ready to be applied (if nothing else, it at least
needs more error checking).

The issue is that locale settings were not inherited by the postgres
backends when they were execed... Instead, the locale was reset to
whatever the system default was. I have a few questions before I
continue fixing up the patch, though:

* Is it enough to explicitly store/save LC_COLLATE and LC_CTYPE, or does
more of the locale stuff need to be stored? I think the rest is handled
by GUC and should thus be reloaded by the GUC routines already, but I'm
not sure there.

* Does pgstat, startup, shutdown, checkpointer and bgwriter need to have
the locale set as well, or can they live with defaults? (my fix only
fixes standard backends, since they have different exec paths)

* Locale can't be changed "on-the-fly", if I'm correct. So just setting
it upon exec should be enough. Or am I wrong there?

//Magnus