aften v0.0.8 is latest released tarball.
https://downloads.sourceforge.net/aften/aften-0.0.8.tar.bz2
Travis builds for OSX use aften v0.0.8 (brew).

More recent aften code has introduced an additional parameter to aften_encode_frame().

The check in wscript compiles a small test program to see if the additional parameter is understood.
If additional parameter 'count' is available, set HAVE_AFTEN_NEW_API.

HAVE_AFTEN_NEW_API is used in common/JackAC3Encoder.cpp to call aften_encode_frame()
either with or without 'count' param.

Problem:
int res = aften_encode_frame(&fAftenContext, fAC3Buffer + SPDIF_HEADER_SIZE, fSampleBuffer);
Fails, because API is
AFTEN_API int aften_encode_frame(AftenContext *s, unsigned char *frame_buffer,const void *samples, int count)

The additional parameter 'count' was added to libaften function aften_encode_frame() here:
e1cbb66628 (diff-d4868af7d235a914aef2ec4f979fcb9fR87)

Solves https://github.com/jackaudio/jack2/issues/455