Add mvkGetRegistryID() function to check OS support for registry ID.
Rename build setting MVK_FORCE_LOW_POWER_GPU to MVK_CONFIG_FORCE_LOW_POWER_GPU
and make it an env var / build setting combo.
Rename env var MVK_LOG_LEVEL to MVK_CONFIG_LOG_LEVEL.
Rename MVKLogging.mm to MVKLogging.cpp.
On iOS, only compile IOSurface support, and link IOSurface framework to
libMoltenVK.dylib, if IPHONEOS_DEPLOYMENT_TARGET is at least iOS 11.0.
Update to latest version of SPIRV-Cross.
Update MoltenVK version to 1.0.15.
via vkGetPipelineCacheData(), vkCreatePipelineCache() & vkMergePipelineCaches().
Add the cereal serialization framework as a dependency.
Update documentation. Update project settings to Xcode 9.3.