RFC: Support non-standard extension (call via casted function pointer)

[Jeff Law]

On 01/26/2016 01:41 AM, Richard Biener wrote:
>
> What I wanted to say is that we preserve the function type used for
> the actual call at least until RTL expansion in gimple_call_fntype.
> I fixed most of the call expansion code to honor that but back ends
> may of course screw up as they still may somehow get at the actual
> DECL called.
I think that's a good thing -- however, I suspect there's m68k backend 
issues that need to be addressed here.  So I think we're roughly on the 
same page.

jeff