Revert "rs: Use -Wno-error - gcc 4.7 adds new warnings rs can't deal with"

This reverts commit eea4ec475f49e85400a0a62ed78665a1bfa8ee2b.
Add -Wno-unknown-warning-option for libRSDriver

Signed-off-by: Paul Beeler <sparksco@gmail.com>

Conflicts:
	Android.mk
Use -Wno-unknown-warning-option for libRs
Signed-off-by: Paul Beeler <sparksco@gmail.com>

Conflicts:
	Android.mk

Conflicts:
	Android.mk