Support for non-string parameterized test parameters#41

It was a bit surprising this wasn't supported. I don't see an easy way (or safe way) to handle pameters that aren't strings. For instance, you can't do this: ``` static int bar_params[] = { 0, 1, 2, 3, 4, 5, MUNIT_PARAMETERS_END }; static MunitParameterEnum test_params[] = { { "bar", bar_params }, { NULL, NULL }, }; ``` Note the use of MUNIT_PARAMETERS_END since NULL would obviously not work (especially given some compilers might resolve that to 0 which is really confusing). Honestly, that wouldn't work so well either (at least, it's not ideal). I would really suggest array lengths be passed instead.