* new models_magicavoxel_loading example

* Portable header-only file "magicavoxel_loader.h" for MagicaVoxel loader example.

* models_magicavoxel_loading example added to CMakeLists.txt and Makefile

* fix models_magicavoxel_loading example for linux.

* * vox_loader into "src/external/vox_loader.h"
 * vox file support for "models.c"
 * updated example "models/models_magicavoxel_loading.c"

* * Fix Vox_FreeArrays (removed memory leak)

* * removed magicavoxel_loader.h

* * Revert vs2019 solution

* * vox_loader.h -> Support custom memory allocators
* vox_loader.h -> Reverse Y<>Z for left to right handed system
* models/models_magicavoxel_loading.c -> fix model center

* * vox_loader.h -> Removed Raylib dependencies

* * Changed Vox_LoadFileName to Vox_LoadFromMemory