Added support for C++11 strongly typed enums

C++11 enum classes were previously not compatible with CHECK_EQUAL and CHECK_ARRAY_EQUAL due to not being implicitly convertable to an int.

eg enum class Colour : short { Red, Blue };

To use uncomment
#define UNITTEST_FORCE_CPP11_DETECTION in Config.h

Test cases for strongly typed enums can be enabled by invoking cmake with -DUTPP_USE_CPP11 option
    CheckEqual(static_cast<std::underlying_type<Expected>::type>(expected), static_cast<std::underlying_type<Actual>::type>(actual))

... I'd question why Expected and Actual are separate template arguments though - does it make sense to check one type of enum against another?