tests: Don't convert \ to / when checking regex's

tests: Don't convert \ to / when checking regex's

When tests compare the output they will try converting backslashes
to slashes to see if that works.  When we compare using regex's,
we can't do that because backslashes can escape special characters.

* tests/test_driver.pl (compare_output): Clean up this function.
(compare_answer_vms) [VMS]: Comparing answers on VMS is complex;
move all of it into its own function returning 0/1.
(compare_answer): A new function to compare answers: return 0/1.
Remember the CRLF->LF conversion forever; only check \ -> / when
we compare strings, not regex's.