Rename module stdalign to stdalign-h. * modules/stdalign-h: Renamed from modules/stdalign. * modules/stdalign-h-tests: Renamed from modules/stdalign-tests. * modules/stdalign-h-c++-tests: Renamed from modules/stdalign-c++-tests. * tests/test-stdalign-h-c++.cc: Renamed from tests/test-stdalign-c++.cc. * doc/posix-headers/stdalign.texi: Update. * modules/stdalign: New file.