Test the requirement of "constexpr" for the deprecation error
Ensure C++11 requirements are checked for the samples build
As @Flamefire noticed, subprojects like "test" and "samples" also need C++11 requirements for their builds to pass (or more accurately, not happen) with C++03 compilers. This adds those requirements for the samples.
This also adds an explicit check on the availability of constexpr to the existing deprecation error, so the problem will be more obvious when someone attempts a manual build. It turns out that msvc-12 supports many parts of C++11 but not that one. Going forward we will need to update the check as we use additional C++11 features.
As @Flamefire noticed, subprojects like "test" and "samples" also need C++11 requirements for their builds to pass (or more accurately, not happen) with C++03 compilers. This adds those requirements for the samples.
This also adds an explicit check on the availability of
constexprto the existing deprecation error, so the problem will be more obvious when someone attempts a manual build. It turns out that msvc-12 supports many parts of C++11 but not that one. Going forward we will need to update the check as we use additional C++11 features.