fcntl-h: rename from fcntl, in preparation for fcntl(2)

fcntl-h: rename from fcntl, in preparation for fcntl(2)

* modules/fcntl: Move <fcntl.h> header replacement...
* modules/fcntl-h: ...to new name, so as not to collide with
like-named function.
* tests/test-fcntl.c: Rename...
* tests/test-fcntl-h.c: ...to this.  Test FD_CLOEXEC.
* modules/fcntl-tests: Rename...
* modules/fcntl-h-tests: ...to this.  Update test file name.
* modules/chdir-long (Depends-on): Update clients.
* modules/chdir-safer (Depends-on): Likewise.
* modules/fcntl-safer (Depends-on): Likewise.
* modules/fts (Depends-on): Likewise.
* modules/mkancesdirs (Depends-on): Likewise.
* modules/mkdir-p (Depends-on): Likewise.
* modules/open (Depends-on): Likewise.
* modules/savewd (Depends-on): Likewise.
* MODULES.html.sh (systems lacking POSIX:2008): Update name.
* doc/posix-headers/fcntl.texi (fcntl.h): Update documentation.

Signed-off-by: Eric Blake <ebb9@byu.net>