use atexit() instead of on_exit() for test
use atexit() instead of on_exit() for test

atexit() is POSIX, whereas on_exit() is not.
Specifically, on_exit() does not exist on
OpenBSD (and perhaps other platforms)

git-svn-id: d023f1085a36f7a677188d00334e37d38ffecf51@1134 64e312b2-a51f-0410-8e61-82d0ca0eb02a

9fcc/check,brarcher/check,libcheck/check,libcheck/check,9fcc/check,krichter722/check,brarcher/check,libcheck/check,libcheck/check,brarcher/check,krichter722/check,9fcc/check,brarcher/check,9fcc/check,brarcher/check,krichter722/check,krichter722/check,9fcc/check,krichter722/check,libcheck/check