Merge branch 'refs/heads/t/clean_server_exit'

Merge branch 'refs/heads/t/clean_server_exit'

This series removes many memory leaks of para_server by refactoring
the shutdown and signal handling code. Most of the leaks happen only
at shutdown and are hence harmless. But it is still good to plug
the leaks because this puts more focus on real memory leaks in the
valgrind output.

The merge conflicted rather badly due to the changes introduced with
the crypt branch that was merged last week. The resolution has been
thoroughly tested, though.

* refs/heads/t/clean_server_exit: (32 commits)
  command.c: Document return value of handle_connect().
  user_list: Make list head static.
  afs: Allow database switching on sighup.
  afs: Free current mood or playlist on exit.
  afs: Free status items on exit.
  afs: Shutdown signals on exit.
  server: Free parse result also in afs.
  afs: Deplete user list at startup.
  server: Free audio file header on exit.
  sender: Deplete ACLs on exit.
  Remove some unused includes from {dccp,http}_send.c.
  server: Make argument of user_list_init() constant.
  server: Deplete user list on exit.
  server: Combine user_list_init() and populate().
  server: Move para_fgets() to user_list.c.
  server: Initialize user list at compile time.
  server: Rename functions related to user lists.
  server: Constify return value of lookup_user().
  server: Let stat command handler perform cleanup on signals.
  server: Have afs process close the current mood on exit().
  ...