GL_EXT_x11_sync_object
https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_x11_sync_object.txt
GL_EXT_x11_sync_object

	GL_SYNC_X11_FENCE_EXT 0x90E1
	GLsync glImportSyncEXT (GLenum external_sync_type, GLintptr external_sync, GLbitfield flags)