connect.c: stricter port validation, silence compiler warning

In addition to checking if the provided port is numeric, also check
that the string isn't empty and that the port number is within the
valid range.  Incidentally, this silences a compiler warning about
ignoring strtol's return value.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

connect.c

diff --git a/connect.c b/connect.c
index 584e04c..2f55ad2 100644
--- a/connect.c
+++ b/connect.c
@@ -480,8 +480,8 @@
 	char *p = strchr(host, ':');
 
 	if (p) {
-		strtol(p+1, &end, 10);
-		if (*end == '\0') {
+		long port = strtol(p + 1, &end, 10);
+		if (end != p + 1 && *end == '\0' && 0 <= port && port < 65536) {
 			*p = '\0';
 			return p+1;
 		}