message: pretend mprotect works
diff: @@ -575,6 +575,9 @@ impl<'a, 'mir, 'tcx: 'mir + 'a> EvalContextExt<'tcx, 'mir> for EvalContext<'a, '
  let addr = self.read_scalar(args[0])?.not_undef()?;
  self.write_scalar(addr, dest)?;
  }
  + "mprotect" => {
  + self.write_null(dest)?;
  + }
  // Windows API subs
  "AddVectoredExceptionHandler" => {
  