Lets keep the environment initialization and conversion section as lean as
possible and move recently added tweaks to setup_windows_environment().
This fixes the following potential problems:
* Prevent duplicate TZ variables if both TZ and MSYS2_TZ are set.
* Some of the higher level x* APIs from wrapper.c require a working
getenv(), using e.g. xstrdup() during initialization is dangerous.
* Slashifying the Windows TMP variable may break native Windows programs,
use POSIX TMPDIR instead.
* Properly slashify TMPDIR even if it is already set, and also if we only
have TEMP, but not TMP.
* Reduce complexity from O(n) to O(log n).
Signed-off-by: Karsten Blees <blees@dcon.de>
f7166d4f6a