t/Util.pm: ensure cmd.exe is in the path on Win32

To pipe, perl must be able to find cmd.exe, so add %SystemRoot%\system32 to the path.
See http://kstruct.com/2006/09/13/perl-taint-mode-and-cmdexe/

This allows tests that use pipe_into_ack() to pass.
Revert "Added a check on the system() call that has been failing"

This reverts commit dcb5bc8ca1cbbd230df6ef3fd58f8ce58babe220.
t/config-finder.t: fix error on Win32

When setting up the global files for Windows, the filenames were not correctly accessed.
t/noenv.t: fix error on Win32

Use File::Spec::splitpath to portably get the directory portion of a path and
use File::Spec::canonpath to portably compare file paths.
Merge pull request #435 from ispedals/testFixes

Windows Test fixes