av: Fix build in ISO C++11 mode

Change-Id: I461d8ce5b24afedee245a6441b600df286c76b63
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
downmix: Fix aliasing violation

Change-Id: I1907da54e9ec40c9afe56c488a974d5286b787e4
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>