[Bug c/87310] -Wc90-c99-compat does not warn about bool usage

[kohanyi.robert at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87310

--- Comment #3 from Róbert Kohányi <kohanyi.robert at gmail dot com> ---
Created attachment 44697
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44697&action=edit
/usr/lib/gcc/x86_64-pc-msys/7.3.0/include/stdbool.h

Here's the referenced <stdbool.h> on Windows using gcc 7.3.0