Add basic qsave/qrestore test.

tests/test-mq-qsave

@@ -0,0 +1,16 b''
+#!/bin/sh
+
+HGRCPATH=$HGTMP/.hgrc; export HGRCPATH
+echo "[extensions]" >> $HGTMP/.hgrc
+echo "mq=" >> $HGTMP/.hgrc
+
+hg init a
+cd a
+
+echo 'base' > base
+hg ci -Ambase -d '1 0'
+
+hg qnew -mmqbase mqbase
+
+hg qsave
+hg qrestore 2

tests/test-mq-qsave.out

@@ -0,0 +1,2 b''
+adding base
+restoring status: hg patches saved state