Merge branch 'refs/heads/t/writer_improvements'

A small set of patches which fix some minor issues, notably a problem
related to the handling of early EOF which affects all paraslash
writers.

* refs/heads/t/writer_improvements:
  alsa_write: Avoid spurious underrun warnings.
  Teach writers to abort gracefully on early EOF.
  alsa_write: Simplify alsa_post_select().

diff --cc NEWS.md
index 7554cd6b9fac8ae061d8be75afa0f4f706007ef8,3e3e7abfda28365cba7abfa2ead1c2c408d75801..76e00d3d166f71a4f98432464b87f937bc28ceaf
--- 1/NEWS.md
--- 2/NEWS.md
+++ b/NEWS.md
@@@ -1,47 -1,6 +1,54 @@@
  NEWS
  ====
  
++---------------------------------------
++0.7.0 (to be announced) "seismic orbit"
++---------------------------------------
++
++- Paraslash writers handle early end-of-file more gracefully.
++- The alsa writer no longer warns about spurious underruns.
++
 +--------------------------------------
 +0.6.4 (2021-11-04) "fuzzy calibration"
 +--------------------------------------
 +
 +This point release contains a fair number of fixes but no new features.
 +This marks the end of the 0.6 development, although paraslash-0.6 will
 +still be supported for some time and subsequent maintenance releases
 +may follow.
 +
 +- The udp sender no longer crashes when empty chunks are encountered.
 +- Fix a double-free bug in the exit path of the server.
 +- The "jmp" command now errors out when given a negative percentage.
 +- A fix for a bug in para_afh which triggered on the attempt to modify
 +  the tags of an invalid mp4 file.
 +- A memory leak in para_afh has been fixed.
 +- The udp sender no longer sends multiple EOF packets.
 +- Some gcc warnings have been silenced.
 +- Minor log level adjustments and documentation improvements.
 +
 +Downloads:
 +[tarball](./releases/paraslash-0.6.4.tar.xz),
 +[signature](./releases/paraslash-0.6.4.tar.xz.asc)
 +
 +---------------------------------------
 +0.5.9 (2021-11-04) "reversed dimension"
 +---------------------------------------
 +
 +This release contains a few important fixes which have accumulated in
 +the maint branch. The paraslash-0.5.x series has now reached its end
 +of life and will no longer be supported. All users should upgrade to
 +a more recent version at this point.
 +
 +- Fix an issue with the bash completion script.
 +- Initialize the random seed also when using libgrypt.
 +- Fix some compiler warnings in the resample filter
 +- Don't return spurious errors from the ff server command.
 +
 +Downloads:
 +[tarball](./releases/paraslash-0.5.9.tar.bz2),
 +[signature](./releases/paraslash-0.5.9.tar.bz2.asc)
 +
  ----------------------------------------
  0.6.3 (2021-02-18) "generalized activity"
  -----------------------------------------