[PATCH] kernel32: Respect the LANG environment variable on Mac OS.

[Charles Davis]

I just realized something. The reason Wine doesn't respect LANG is that
it overrides the LC_MESSAGES setting if it is set to the default. It
will be set to the default if there is no LC_MESSAGES in the
environment. So we don't want to override LC_MESSAGES if there's a LANG
variable in the environment. Besides, why do all that work if we're not
going to override LANG anyway if it's already set?