Merge branch 'refs/heads/t/opus'

This series abstracts out the custom header concept of ogg/vorbis
streams and introduces a public API for it. The new API is employed
for ogg/opus streams to guarantee that fixed size audio format headers
are used for streaming.

Cooking for six weeks.

* refs/heads/t/opus:
  opus_afh: Use custom header API to strip comment packet.
  ogg: Abstract out custom header code.
  Prefix public functions of ogg_afh_common.c with "oac".
  afh_recv: Downgrade severity of log message.

diff --combined NEWS.md
index d9f092c93003d764f85723369d53ee717b6594e9,5398d3a53a423716b0243a7543f9a3bbd15c1162..6724317d1adfa356de71242934336e8c32343beb
--- 1/NEWS.md
--- 2/NEWS.md
+++ b/NEWS.md
@@@ -1,24 -1,15 +1,25 @@@
  NEWS
  ====
 +---------------------
 +current master branch
 +---------------------
  
 -------------------------------------------------
 -0.6.1 (to be announced) "hyperbolic correlation"
 -------------------------------------------------
 -
 +- New sort order for the ls command: -s=h sorts the ls output by hash
 +  value of the audio file.
 +- autogen.sh now runs the test suite after a successful build.
  - The contents of overview.pdf have been integrated into the user
    manual.
++- Fixed sized audio format headers for ogg/opus streams.
  - The doxygen source browser has been disabled temporarily. The
    API reference is still online, though.
  - Overhaul of the source code documentation.
 +- The deprecated --full-path option of the ls command has been
 +  removed. It was a no-op since 0.6.0.
 +- The wma decoder has been cleaned up and its bitstream API made
 +  more robust.
 +- The image/lyrics ID status items of the current audio file are now
 +  updated on changes. This affects para_gui, which used to report the
 +  old value until EOF.
  
  -------------------------------
  0.6.0 (2017-04-28) "fuzzy flux"