Merge topic branch t/play into pu

Merge topic branch t/play into pu

This small series contains a few minor tweaks for para_play. The most
obvious change is that para_play is no longer built on systems which
lack libreadline.

<!--
- para_play is no longer built if libreadline is not installed.
-->

* refs/heads/t/play:
  play: Shut down alsa on input EOF.
  play: Simplify and improve get_key_map_seq().
  play: Remove pointless goto in play_post_monitor().
  Return from filter_setup() so callers can reset the terminal.
  Let para_play depend on libreadline.

# Conflicts:
#	configure.ac
#	play.c
#	web/manual.md