procedure.
(newlib_pass_fail): Change to compile and run only one file.
* testsuite/newlib.locale/locale.exp: Use new
newlib_pass_fail_all procedure.
* testsuite/newlib.string/string.exp: Likewise.
* testsuite/newlib.stdlib/atexit.c: New file.
* testsuite/newlib.stdlib/atexit.exp: Ditto.
* testsuite/newlib.string/tstring.c: Change default start size
to something more reasonable for embedded platforms.