Following gcc behaviour with regards to calling conventions on x86_64

http://blogs.msdn.com/freik/archive/2005/03/17/398200.aspx

Right now, if anything other than ccall is given to ghc on x86_64 architectures, ghc errors out with the complaint that the calling convention is not supported on this architecture. gcc on the other hand, handles this situation gracefully, ignoring the calling convention attribute. My thought is that ghc should do this as well.

Currently, I get this:

TerraHS/TerraLib/TePoint.hs:121:0:
    calling convention not supported on this architecture: stdcall
    When checking declaration:
        foreign import stdcall unsafe "static  &c_tepoint_setobjectid" tepoint_setobjectid
          :: TePointPtr -> CString -> IO ()

I think I should instead get a warning saying that the calling convention is being ignored.