Manual test registration due to unavailability of static initialization

[basvodde]

Some environments might not have static initialization. For these cases, having a good way for manual registration might be useful.

As there is so much might in this issue, it might not be the best time to implement this yet. If you read this and need this, let us know :)

[arstrube]

Doesn't TEST_GROUP_C_WRAPPER() provide something like that, at least for test cases using the _C macros?

[basvodde]

Yeah, but for C++ :)