[PATCH] Fix some ghci way testsuite failures on Windows

On my 32bit Windows make fulltest run I got these two failures: ../../libraries/directory/tests getDirContents002 [bad stdout or stderr] (ghci) ../../libraries/process/tests process004 [bad stdout or stderr] (ghci) The problem here is that although the respective all.T files have normalise_exe, However, check_stderr_ok only normalizes away '.exe' when platform override files DO NOT exist and these test cases have platform overrides for mingw32. This seems like something to add a helper function for in testlib.py. Here's the patches for one way to accomplish fixing the problem. Fyi, Bill