LegacyCamera: Fix build in ISO C++11 mode

Fixes building with -std=gnu++11 - this is useful for compatibility
with future compilers (where gnu++11 will be the default mode) and
to make additional language features/optimizations (e.g. constexpr)
available.

Change-Id: I4b0bd843731370e205c8bef4a313e7244d2ca5de
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>