tests: test some of the *-safer modules

tests: test some of the *-safer modules

* modules/fopen-safer (Depends-on): Add fopen.
* modules/fcntl-safer (Depends-on): Add fcntl.
* modules/stdlib-safer (Depends-on): Add stdlib.
(configure.ac): Set indicator.
* modules/unistd-safer (configure.ac): Likewise.
* modules/tmpfile-safer (configure.ac): Likewise.
(Depends-on): Add tmpfile.
* lib/stdio--.h (fopen, tmpfile): Don't override unless module is
active.
* tests/test-fopen.c (includes): Test safer versions when they are
in use.
* tests/test-open.c (includes): Likewise.

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