Implement basic ANDROID_image_native_buffer support.

Change-Id: I7e844eb7c313455d48cd2fc09440f10d639b4c77
Reviewed-on: https://swiftshader-review.googlesource.com/2758
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Greg Hartman <ghartman@google.com>
Reviewed-by: Ping-Hao Wu <pinghao@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>