loader: xglEnumerateLayers() returns layer names rather than library names
loader: xglEnumerateLayers() returns layer names rather than library names

Loader's xglEnumerateLayers calls into each layer library to get their
layer names from the library.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools