Merge branch 'refs/heads/t/mp4ff'

Merge branch 'refs/heads/t/mp4ff'

This 140 patch behemoth adds a stripped down copy of libmp4ff to the
repo. This has become necessary because the library was dropped from
the faad project.

The series starts with a patch which adds an unmodified copy of the
relevant parts of libmp4ff to the repo. All code is combined in a
single file, mp4.c, which contains approximately 2K lines of code. The
public API is defined in the new mp4.h.

The remaining patches clean up the two new files, simplifying and
removing large parts of it. Some of the patches modify the API,
and those require small changes to the aac audio format handler,
which also becomes simpler due to these changes. The aac decoder,
however, is not touched in this series.

* refs/heads/t/mp4ff: (140 commits)
  mp4: Don't abort on truncated files.
  mp4: Document the purpose of each atom.
  mp4: Doxify the public API.
  mp4: Check for missing metadata also for regular opens.
  mp4: Rename mp4_open_read() to mp4_open().
  mp4: Rename mp4_meta_update() to mp4_update_meta().
  mp4: Simplify mp4_num_samples().
  mp4: Reject files with zero time scale.
  mp4: Assorted trivial cleanups.
  mp4: Remove ->len member of struct mp4_tag.
  mp4: Fix possible memory leak on errors.
  mp4: Return proper types for sample rate and count.
  mp4: Fail early on invalid sample rate or sample count.
  mp4: Remove E_MP4_BAD_CHANNEL_COUNT.
  mp4: Improve mp4_get_sample_size().
  mp4: Make sample number be an unsigned parameter.
  mp4: Check the return value of ->truncate().
  mp4: Make most loop variables unsigned.
  mp4: Replace the five tag value functions by a single one.
  mp4: Provide proper error codes for all errors.
  ...