Fix the following bug submitted by Justin Handville.

int main(int argc, char* argv[])
{
  return 0;
}

After speaking briefly with Chris, we decided this should be a front-end fix.

The fix...have Sema::GetTypeForDeclarator() do the default function/array conversion, as
I outlined in the 9/9 email on this topic.

Since this conversion is done before Sema::ParseParamDeclarator(), I thought I could
remove the conversion from Sema::ParseParamDeclarator(). Unfortunately, this didn't work.
The conversion apparently needs to be done in both places (which doesn't make sense to me).

Will investigate.

llvm-svn: 41811