rs: Fix build with ISO C++ 11 compilers

ISO C++ 11 no longer allows implicit narrowing during initialization

Change-Id: Iec3726fc12379e17300a372619378b77d033d841
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
rs: Use -Wno-error - gcc 4.7 adds new warnings rs can't deal with

Change-Id: I38fe66629552d6f11be1bb69d5a93a05251614df
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>