Rewrite error on functions with attributes

[john-h-kastner]

For example in this test case

void foo( const char *fmt, __builtin_ms_va_list argp);
__attribute__((ms_abi)) void bar ( const char *fmt, ...)  {
  __builtin_ms_va_list argp;
  __builtin_ms_va_start(argp, fmt);
  foo(fmt, argp);
  __builtin_ms_va_end(argp);
}

bar becomes (const char *fmt : itype(_Ptr<const char>), ...) {