{testing/aptdec, testing/cm256cc, testing/serialdv, testing/sdrangel): new aport(s)

This merge-request aims to provide sdrangel(https://github.com/f4exb/sdrangel/releases) to Alpine, a popular Software-Defined Radio GUI application, it also contains aptdec, cm256cc and serialdv that are required for a proper build of the aforementioned package. I can resubmit separate merge-requests if necessary.

Thanks :)