JT4 enablement

[sq6emm]

This is fixing #373

[jketterl]

Thank you for the pull request. The change looks good overall, just needs a final polishing pass, please see inline comments. Please also check the question about a potential impact on CPU usage by the increase in frequency tolerance. Cheers!

[sq6emm]

@jketterl how do you think, is it now old enough to be merged?:)

[jketterl]

Has there been any updates?

[sq6emm]

Well I believe for basic functionality nothing more needed? Decoding of JT4 is currently based on the default bandwidth. I also checked as you requested the CPU Increase and described them so you can decide if to implement a possibility to modify the decode bandwidth (that I consider as a feature update)... So well is there anything missing?

[jketterl]

Your initial response to the discussion about the -F parameter was:

This is needed capability especially on uWaves where frequencies are not stable enough.

This gave me the impression that being able to control the frequency tolerance was essential to this feature. As such, I did not consider merging this for as long as this setting is not available.

[sq6emm]

It's true, but with agile approach it's better to have a MVP;)

[sq6emm]

@jketterl any chance to merge it?

[jketterl]

Do you see any change? Did you do any changes yourself?