scripts: Added -! as a short-form for --everything

-!/--everything has been useful enough to warrant a short form flag,
and -! is unlikely to conflict with other flags while also getting the
point across that this is a bit of an unusual option.

scripts/ctx.py

@@ -1517,7 +1517,7 @@ if __name__ == "__main__":
             help="Include internal symbols. Useful for introspection, but "
                 "usually you don't care about these.")
     parser.add_argument(
-            '--everything',
+            '-!', '--everything',
             action='store_true',
             help="Include builtin and libc specific symbols.")
     parser.add_argument(