CFTimeZone: name and abbreviate GMT offsets like Apple#138

DTW-Thalion wants to merge 2 commits into

gnustep:mastergnustep/libs-corebase:masterfrom

DTW-Thalion:fix/cftimezone-gmt-abbrevDTW-Thalion/libs-corebase:fix/cftimezone-gmt-abbrevCopy head branch name to clipboard