plugin-api.h patch to add a new interface for linker plugins

[Cary Coutant]

> Ping.  Is this alright to apply now or should I wait for Stage 1?
>
> * plugin-api.h (ld_plugin_get_wrap_symbols): New
>   plugin interface.

I'd say go ahead and apply the patch in binutils, and wait for Stage 1
to sync back to GCC, unless someone there OKs it sooner.

Nick, is that OK?

-cary