* Source/NSTimeZone.m: Include system tzfile.h if found.
(abbreviationMap): Add abbreviation from systemTimeZone if not
already there.
(systemTimeZone): Update the search list to look for time zone in TZ,
then system location, then tznam.
(getTimeZoneFile:): Look for file in system directory first.
* Source/nstzfile.h: Renamed from tzfile.h
git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@20217 72102866-910b-0410-8b05-ffd578937521