Not all messages have structures and we need to unref messages
when returning GST_BUS_DROP in the sync bus handler.

Detect EOS faster.
Try to reuse one of the input buffer as the output buffer. This usually works
and avoids an allocation and a memcpy.
Be smarter with GAP buffers so that they don't get mixed or cleared at all. Also
try to use a GAP buffer as the output buffer when all input buffers are GAP
buffers.

Install a clipping function in the collectpads and use the audio clipping helper
function to perform clipping to the segment boundaries.

Fixes #590265

Don't leak the queue and typefind elements that we might link after the
source element.

There is no reason to name the queue.

Fixes #605219

Add functions to convert SDES names to their types and back. Will be used later
to set SDES items using a GstStructure.

See #595265

From 47cb23a to 14cec89

Fixes #605100.

Added drop-frames, cap-overflow, cap-underflow, and rate-buffer.

Increase default drift tolerance to 40ms to avoid glitches with decoders
or formats where there's a lot of timestamp jitter for some reason or
another (in this case: asf/wma), at least until we implement timestamp
smoothing.

It may not be uncommon for the input timestamps to experience some jitter
around the 'perfect time'.  As such, instead of regularly adding and dropping
samples, optionally allow for some tolerance in a more relaxed approach.

API: GstAudioRate:tolerance

Do not compare a media (buffer) time to a (bogus) running time
(or their offset equivalents).

g_mapped_file_unref() was introduced in GLib 2.22, but we depend
only on GLib 2.18, so use g_mapped_file_free() when compiling
against older GLib versions until we bump the GLib dependency.

Add some utility functions for language tags and ISO-639
codes. These are useful for both GUIs and elements. The
iso-codes package is used for language name translations
if available.

API: gst_tag_get_language_codes()
API: gst_tag_get_language_name()
API: gst_tag_get_language_code()
API: gst_tag_get_language_code_iso_639_1()
API: gst_tag_get_language_code_iso_639_2B()
API: gst_tag_get_language_code_iso_639_2T()

When unlocking, we set the flushing state on the fdset. Implement unlock_stop so
that we can use it to unset the flushing state again.

Fixes #577326

Remove all granulepos hacks and simply use the timestamps from the new oggdemux
like any other decoder.