Use CMAKE_SYSTEM_NAME to isolate Linux-specific setup.
Use require_app/APP_LIBRARY to pull in platform-specfic libs like X11.
Add Darwin build setup.
Add pxfmt_gl.h to simplify platform-specific GL header includes.
Skip unsupported texture formats for Mac.
Update console_output_func parameters to match prototype.
Define VOGL_PLATFORM_HAS_UINT and VOGL_PLATFORM_HAS_SDL for Mac.
Set up Mac API/GL build constants (VOGL_USE_OSX_API and VOGL_PLATFORM_HAS_CGL).
Declare Mac GL types and provide Win32 types supplied by X11 on Linux.
Use PLATFORM_LINUX/VOGL_USE_LINUX_API rather than PLATFORM_POSIX/COMPILER_GCCLIKE for Linux-specific code.
Use pxfmt_gl.h for portable include of gl.h.
Linux and Mac are both LP64.
Add some unimplemented CGL stubs in voglcommon for Mac.
Mac implementation of file_utils::get_exec_filename.
Mac implementation of get_proc_cmdline.
Mac implementation of vogl_tracked_check_heap.
Use 64-bit capable FILE apis for Mac.
Mac implementation of plat_get_system_gl_module_name.
Use reinterpret_cast+uintptr_t to convert pthread_t to uint64_t, pthread_t is a pointer on the Mac.
Use Mac/Linux-specific names for sysconf page size value.