include signal.h in exit tests
include signal.h in exit tests

technically this should have been here before. However, the
autotools build did not need it, so it was not caught.
The CMake build requires it be in place to get the definition
of the SIGSEGV signal.

git-svn-id: d023f1085a36f7a677188d00334e37d38ffecf51@1123 64e312b2-a51f-0410-8e61-82d0ca0eb02a

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