patch 8.1.1261: no error for quickfix commands with negative range

Problem:    No error for quickfix commands with negative range.
Solution:   Add ADDR_UNSIGNED and use it for quickfix commands.  Make
            assert_fails() show the command if the error doesn't match.

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1261,
 /**/
     1260,
 /**/