Merge branch 't/sched_improvements'

diff --cc NEWS
index a9572d7b45de854b175f2c581668dc6091243941,c6c2e4dbd741954bd344d5b240e7ba98851ff7e8..f76a6e97c1ed9e6d27ddb91a7637b2e550c35fbe
--- 1/NEWS
--- 2/NEWS
+++ b/NEWS
@@@ -17,7 -7,6 +17,8 @@@ are the highlights of this release
          to replace 5 lines in the config file (one for each audio
          format) by one single line. See the manual for details.
        - Compiles cleanly also with llvm/clang.
 +      - Corrupt mp3 files are handled more gracefully.
++      - sched: Optimized zero timeouts.
  
  --------------------------------------
  0.4.7 (2011-06-01) "infinite rollback"