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

openstrike/ack2,petdance/ack2,gregory-nisbet/ack2,gregory-nisbet/ack2,openstrike/ack2,shlomif/ack2,petdance/ack2,gregory-nisbet/ack2,karenetheridge/App-Ack,gregory-nisbet/ack2,h3xx/ack2,h3xx/ack2,openstrike/ack2,karenetheridge/App-Ack,petdance/ack2,petdance/ack2,gregory-nisbet/ack2,openstrike/ack2,packy/ack2,h3xx/ack2,gregory-nisbet/ack2,karenetheridge/App-Ack,packy/ack2,shlomif/ack2,shlomif/ack2,shlomif/ack2,openstrike/ack2,openstrike/ack2,openstrike/ack2,karenetheridge/App-Ack,h3xx/ack2,gregory-nisbet/ack2,h3xx/ack2,packy/ack2,packy/ack2,packy/ack2,shlomif/ack2,karenetheridge/App-Ack,h3xx/ack2,packy/ack2,h3xx/ack2,packy/ack2,packy/ack2,gregory-nisbet/ack2,karenetheridge/App-Ack,shlomif/ack2,petdance/ack2,karenetheridge/App-Ack,petdance/ack2,petdance/ack2,karenetheridge/App-Ack,openstrike/ack2,h3xx/ack2,petdance/ack2