loader: implement new layer init method

loader: implement new layer init method

New layer init method requires the construction of
Link information for CreateInstance and CreateDevice
that is accessible to layers via the CreateInfo.pNext pointer.
The layer can then use the Get*ProcAddr from the Link
structure to initialize their dispatch table if the
call down the chain returns successfully.
This removes the need to do special initialization work
at Get*ProcAddr time.
Layer Get*ProcAddr now return their internal function
pointers regardless of the value of instance or device.
Only need to have valid instance & device when looking
up extensions or when passing the request down the chain.
This mechanism allows us to remove object wrapping used
by the loader previously. Also simplifies the dispatch table
setup.

Conflicts:
	layers/device_limits.cpp
	layers/draw_state.cpp
	loader/loader.c
	loader/trampoline.c