Support for building on native windows with cmake

[Rob2309]

This PR aims to support natively building on windows via cmake. Currently, a debug and release build should work on a windows machine with the required dependencies built from source with cmake. The only external dependency that has to be manually installed is OpenAL.

On top of that, multiple instances of undefined behavior and/or unportable code were fixed.

The cmake option ENABLE_STEAMWORKS was also added and building without steamworks is supported.