diff 'rename' format change.

Clearly even Junio felt git "rename" header lines should say "from/to"
instead of "old/new", since he wrote the documentation that way.

This way it also matches "copy".

git-apply will accept both versions, at least for a while.

diff.c

@@ -786,8 +786,8 @@ static void diff_flush_patch(struct diff_filepair *p)
 	case 'R':
 		sprintf(msg_,
 			"similarity index %d%%\n"
-			"rename old %s\n"
-			"rename new %s",
+			"rename from %s\n"
+			"rename to %s",
 			(int)(0.5 + p->score * 100.0/MAX_SCORE),
 			p->one->path, p->two->path);
 		msg = msg_;