Also, provide a memory-safe overload called ggwave_ndecode()
The overload takes an extra parameter that specifies the size of
the output buffer and thus limits the size of the Rx payload that can be
decoded and stored.
* ggwave : add interface for changing ggwave's internal logging
Using GGWave::setLogFile() it is now possible to change the log file
used internally by ggwave, or disable it all together.
* ggwave : add comments about thread-safety of setLogFile
