Fix build of plugin-disabled ld

[Richard Sandiford]

"Joseph S. Myers" <joseph@codesourcery.com> writes:
> 2011-03-23  Joseph Myers  <joseph@codesourcery.com>
>
> 	* lexsup.c (parse_args): Only set report_plugin_symbols if plugins
> 	are enabled.  Mark level as possibly unused.

OK, thanks.

Richard