[Ham-Mac] proposed changes in 8psk modes

[w1hkj]

The following changes are proposed for inclusion in the next public 
release of fldigi

     8PSK FEC CPU reduction
      * NOTE: 8PSK 125F and 250F are not compatible with previous versions!
        - all other 8PSK modes retain backwards compatability

      * Lowered CPU requirements to allow for use on Android/Netbook 
devices:
        - Lowered 8PSK 125F and 250F to constraint length 13 FEC
        - Adjusted maximum traceback memory for viterbi decoder
        - Set traceback to an optimally-high value in viterbi.cxx 
constructor
        - 8PSK - 500F 1000F & 1200F now use only 1 viterbi decoder 
without voting

These changes are specifically to reduce cpu usage on AndFlmsg (Android 
flmsg/fldigi application).  Please respond to both John Phelps, KL4YFD, 
and myself if these changes will adversely effect your current operation 
or seriously impact your code base.

Thank you.

Dave, W1HKJ