Make win32tzlist.pl checkable again
Commit
1301c80b21 removed some infrastructure needed to check
windows-oriented perl scripts. It also removed most such scripts, but
this one was left over. We repair the damage by making Win32::Registry a
conditional requirement that is only loaded on Windows. With this change
`perl -cw win32tzlist.pl` once again passes on non-Windows machines.
Discussion: https://postgr.es/m/
a2bd77fd-61b8-4c2b-b12e-
3e22ae260f82@eisentraut.org