command: allow to omit END in ranges (START:END)

If END is omitted, mpd should use the highest possible value instead of raising an error.
This partially reverts 52e9cab1c1

NEWS

@@ -1,4 +1,6 @@
 ver 0.17.4 (2013/??/??)
+* protocol:
+  - allow to omit END in ranges (START:END)
 * decoder:
   - ffmpeg: support float planar audio (ffmpeg 1.1)
 * player:

src/protocol/argparser.c

@@ -103,7 +103,7 @@ check_range(struct client *client, unsigned *value_r1, unsigned *value_r2,
 
 	if (*test == ':') {
 		value = strtol(++test, &test2, 10);
-		if (test2 == test || *test2 != '\0') {
+		if (*test2 != '\0') {
 			command_error(client, ACK_ERROR_ARG,
 				      "Integer or range expected: %s", s);
 			return false;