[Bug c/66298] -Wmisleading-indentation should also detect missing indentation

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66298

--- Comment #3 from Florian Weimer <fw at gcc dot gnu.org> ---
This would also help to detect the incorrect pragma placement in bug 63326:

int main()
{
  int result = 1;
  if (result < 0)
#pragma GCC diagnostic ignored "-Wunused-result"
    return result;
  return 0;
}