silence warning about ck_do_nothing being able to return
silence warning about ck_do_nothing being able to return

The prototype for ck_do_nothing marks it as noreturn.
gcc thought that the function could still return. Adding
an exit() call at the end (although the assert() will not
let it get that far) to silence the warning.

git-svn-id: d023f1085a36f7a677188d00334e37d38ffecf51@828 64e312b2-a51f-0410-8e61-82d0ca0eb02a

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