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

This reverts commit a3cf90c808fe5a6a4e8a20b2e9b3e48c180f3e7c.

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

Conflicts:
	Android.mk
Add -Wno-unknown-warning-option for libRSDriver

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