Align MOC with the 2014-02-28 Autoconf archive.

git-svn-id: svn://daper.net/moc/trunk@2697 910807d9-36e0-0310-a014-e9ea483e2ba4
Replace custom shell code with Autoconf archive macros.

git-svn-id: svn://daper.net/moc/trunk@2698 910807d9-36e0-0310-a014-e9ea483e2ba4
Remove obsolete configure test for dirent header.

According to the Autoconf documentation:

  "This macro is obsolescent, as all current systems with directory
   libraries have `<dirent.h>'.  New programs need not use this macro."

I guess we'll find out the accuracy of this statement in due course.

git-svn-id: svn://daper.net/moc/trunk@2699 910807d9-36e0-0310-a014-e9ea483e2ba4
Replace custom shell code with Autoconf version-comparison macro.

git-svn-id: svn://daper.net/moc/trunk@2700 910807d9-36e0-0310-a014-e9ea483e2ba4
Warn of raising the minimum TagLib requirement to version 1.5.

This is the first known version in which pkg-config files are installed,
which will soon be used to replace taglib-config.

git-svn-id: svn://daper.net/moc/trunk@2701 910807d9-36e0-0310-a014-e9ea483e2ba4
Decouple mono-mixing ('J') from softmixer ('w').

Also see: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=621797

git-svn-id: svn://daper.net/moc/trunk@2702 910807d9-36e0-0310-a014-e9ea483e2ba4