* lib/fsync.c: New file.
* m4/fsync.m4: New file.
* modules/fsync: New file.
* modules/fsync-tests: New file.
* tests/test-fsync.c: New file.
* modules/unistd: Substitute GNULIB_FSYNC and HAVE_FSYNC.
* m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Define and AC_SUBST
both GNULIB_FSYNC and HAVE_FSYNC.
* lib/unistd.in.h (@GNULIB_FSYNC@): Add a block for fsync.
* MODULES.html.sh (posix_functions): Add fsync.
* doc/posix-functions/fsync.texi: Update.