We're pretty careful about using const these days, so
enable these warnings to keep us that way.

* Correctly define the following CPP directives:
  HAVE_FAAD_BUFLEN_FUNCS
  HAVE_MP4AUDIOSPECIFICCONFIG

* link against libwavpack correctly in bs

* fix include path for the mpd config.h for mp4ff

git-svn-id: https://svn.musicpd.org/mpd/trunk@7399 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Dealing with autotools is too painful when having
to deal with multiple build environments and
configurations.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7368 09075e82-0dd4-0310-85a5-a0d7c8717e4f