Enhancement Request: Support Enhanced MDC "EMC" from Icom

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Icom has extended the standard MDC-1200 protocol to include free-form messages, 
diagnostic polling, and GPS data, which would be nice to be able to decode via 
software. I can provide discriminator audio samples with known data payloads to 
simplify the process. I'd also like to see a way to output raw opcodes even if 
they're unknown so future enhancements to the MDC-1200 protocol can be decoded, 
even if the library doesn't explicitly support it.

Thanks!

Original issue reported on code.google.com by [email protected] on 9 Jan 2015 at 7:20