mergetools: add alternate registry keys for 32bit apps on 64bit O/S
Not all applications needed the workarounds, so I did not add alternate keys for
every Windows merge application.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state