Camera: ISO C++11 build fixes

Fix build in ISO C++11 mode:
- enum typesafety
- constexpr

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
Merge branch 'linaro_android_4.2.1' of http://android.git.linaro.org/git-ro/platform/packages/apps/Camera into jb-mv-wip