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.

When we have a source with subtitles but they were disabled with the flags,
still ghostpad the video pad instead of leaving it unlinked.

don't update the slider a 100 times a second, it's likely higher than the screen
framerate and just wastes cpu.

Remove the granulepos hacking now that oggdemux outputs timestamps like any
other demuxer.

When iterating the list and removing the current element, first
get the next element and then remove the current one and not
the other way around.

Improve keyframe seeking.
Fix reverse playback.

Implement keyframe seeking in oggdemux by doing the double seek trick. First
seek to the required position, then read pages for all streams to grab the
granulepos (to know the timing of the keyframe) of each stream, then seek back
to the first keyframe.

After a seek, discard all packets before the packet with the granulepos on it so
that the output buffers contain valid timestamps.

Reorder some code so that we check the timestamps before allocating and pushing
an output buffer.

Do more checks on valid packets in ogm mode.

When the current granulepos is unknown and set to -1, don't try to add durations
to it.

Clamp the initial granulepos to 0 instead of going negative for some badly muxed
ogg files.

Do some additional checks on the granulpos timestamp before using it for
calculating the duration because oggdemux generates wrong granulepos now.
Fixes seeking somewhat again.

OGM demuxing no longer requires helper elements.  It's done internally
in oggdemux.  Vorbis comments are still not handled because I don't
have anything to test with.

Because we can.

gstoggstream.c:419: error: format ‘%lld’ expects type ‘long long int’, but argument 8 has type ‘gint64’
gstoggdemux.c:2253: error: format ‘%lld’ expects type ‘long long int’, but argument 8 has type ‘GstClockTime’
gstoggdemux.c:2333: error: format ‘%lld’ expects type ‘long long int’, but argument 8 has type ‘GstClockTime’

Fixes some printf format strings to make it build on mac.

When debugging is disabled, we won't see anything printed anyway.

Currently supporting timescale, timestamps, font, size,
textColor, backColor, plain, bold and italic

Fixes #603357