This is a very outdated copy of Bullet's btScalar.h,
we're probably only discovering the tip of the bad
cross-platform compatibility of the unmaintained vhacd.
On some systems, including Alpine Linux, musl is used instead of
glibc. This commit patches the third-party V-HACD module to provide
a macro not provided by musl.
Fixes#31555.
Godot-specific changes will then be redone without touching upstream formatting.
Also documented current state in thirdparty/README.md and added LICENSE.
Add vhacd to COPYRIGHT.txt.
