Deprecate merge-recursive.py

This renames merge-recursive written in Python to merge-recursive-old,
and makes merge-recur as a synonym to merge-recursive.  We do not remove
merge-recur yet, but we will remove merge-recur and merge-recursive-old
in a few releases down the road.

Signed-off-by: Junio C Hamano <junkio@cox.net>

t/test-lib.sh

@@ -211,7 +211,7 @@ export PATH GIT_EXEC_PATH
 PYTHON=`sed -e '1{
 	s/^#!//
 	q
-}' ../git-merge-recursive` || {
+}' ../git-merge-recursive-old` || {
 	error "You haven't built things yet, have you?"
 }
 "$PYTHON" -c 'import subprocess' 2>/dev/null || {