xmlSaveUri() incorrectly recomposes URIs with rootless paths

For https://bugzilla.gnome.org/show_bug.cgi?id=731063

xmlSaveUri() of libxml2 (snapshot 2014-05-31 and earlier) returns
bogus values when called with URIs that have rootless paths
(e.g. "urx🅱️b" becomes "urx://b%3Ab" where "urx:b%3Ab" would be
correct)

uri.c

@@ -1194,8 +1194,6 @@ xmlSaveUri(xmlURIPtr uri) {
                 if (temp == NULL) goto mem_error;
                 ret = temp;
 	    }
-	    ret[len++] = '/';
-	    ret[len++] = '/';
 	}
 	if (uri->path != NULL) {
 	    p = uri->path;