test-debugextensions: add dummy extension to make ifcontains() test more solid
If testedwith were a string, ifcontains("3.2", testedwith) would match "3.2.1".
New test added to cover that.
$ 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