Rename module 'strftime' to 'nstrftime'. * m4/nstrftime.m4: Renamed from m4/strftime.m4. * lib/nstrftime.c: Renamed from lib/strftime.c. * modules/nstrftime: Renamed from modules/strftime. (Files, Makefile.am): Update. * tests/test-nstrftime.c: Renamed from tests/test-strftime.c. Fix comment. * modules/nstrftime-tests: Renamed from modules/strftime-tests. (Files, Makefile.am): Update. * modules/strftime: New file, an obsolete indirection. * doc/posix-functions/strftime.texi: Update reference. * config/srclist.txt: Update info.