NNAPI Support Library

Files in this directory are a copy of NNAPI Support Library files in AOSP.

The files had to be modified to make them work in TF Lite context. Here is the list of differences from the AOSP version:

#include directives use fully-qualified paths.
#pragma once directives are changed to header guards. Android paths in header guards are changed to TF Lite paths.
tensorflow/lite/nnapi/NeuralNetworksTypes.h is used for definitions of NNAPI types instead of NeuralNetworksTypes.h from AOSP.
loadNnApiSupportLibrary(...) is using tensorflow/lite/minimal_logging.h for logging on errors.
SupportLibrary.h declarations are wrapped into tflite::nnapi namespace.
__BEGIN_DECLS and __END_DECLS are changed to explicit extern "C" blocks.
Copyright notice is changed to the one used in Tensorflow project.