Merge pull request #8 from atsb/sdl3

Initial SDL3 support

Doing proper multiplatform agnostic macros

Because of the way this mess was done, for macOS and linux the old WINAPI functions were used but were replaced with POSIX calls.  So we will use the WINAPI for Windows and the 'fake' WINAPI for UNIX systems (with AVP in the name).

adding more resolutions that are also compatible with various Mac models

Merge branch 'main' of github.com:atsb/NakedAVP into main