gitweb: refer to picon/gravatar images over the same scheme

With the current code, the images from picon and gravatar are
requested over http://, and browsers give mixed contents warning
when gitweb is served over https://.

Just drop the scheme: part from the URL, so that these external
sites are accessed over https:// in such a case.

Signed-off-by: Andrej E Baranov <admin@andrej-andb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -2068,7 +2068,7 @@ sub picon_url {
 	if (!$avatar_cache{$email}) {
 		my ($user, $domain) = split('@', $email);
 		$avatar_cache{$email} =
-			"http://www.cs.indiana.edu/cgi-pub/kinzler/piconsearch.cgi/" .
+			"//www.cs.indiana.edu/cgi-pub/kinzler/piconsearch.cgi/" .
 			"$domain/$user/" .
 			"users+domains+unknown/up/single";
 	}
@@ -2083,7 +2083,7 @@ sub gravatar_url {
 	my $email = lc shift;
 	my $size = shift;
 	$avatar_cache{$email} ||=
-		"http://www.gravatar.com/avatar/" .
+		"//www.gravatar.com/avatar/" .
 			Digest::MD5::md5_hex($email) . "?s=";
 	return $avatar_cache{$email} . $size;
 }