OTHER: Cleanup

Re-enabled nellymoser (ffmpeg appears to be okay with it now)

Fixed possible infinite loop in the code that handles the data (if any)
between the header and tag data.
OTHER: Rename constants to something more readable
BUG(2276): Set duration proper

This adds an AMF reader which allows us access to
onMetaData's duration object and lets people see some interesting info
in the log if they ran xmms2d -v.

Also cleaned up byte swapping functions.
BUG(2276): Check if duration is already set
OTHER: AAC support

flv now supports AAC (thanks to juhovh for reminding me
that I changed some _peek calls to _read)

Split header reading code into another function. A nice side effect
of the AAC support.
OTHER: Isolate valgrind check from xcu and add error check.
OTHER: Add memory check to medialib-runner.
OTHER: Exit with failure if medialib-runner tests fail.
OTHER: Add test name to the valgrind logs.
OTHER: Bump src/lib/s4

* src/lib/s4 1800e39...1643912 (1):
  > OTHER: Update test tools to match XMMS2.