Make headers C++11 compatible.

C++11 states that any non-integral static member of a class must be
defined as constexpr. Unfortunately, prior to C++11 there is no
constexpr. As such, use a compatibility macro to use constexpr only
when using C++11 or newer.

Bug: 18466763
Change-Id: Id7cd05b7531d93b6d3e80434e1e7029019d11580
2 files changed