mp_tags: move generic mp_tags stuff into its own .c/.h files in common/

rename add_metadata to the more genera/descriptive mp_tags_copy_items_from_av_dictionary

Signed-off-by: wm4 <wm4@nowhere>
talloc README: more human readible api reference
vf: add vf_control_by_label to send vfctrl to specific filter
vf: auto-label video filters if no label is specified

Signed-off-by: wm4 <wm4@nowhere>
vf_lavfi: fix ffmpeg deprecation warning for avfilter_graph_parse

use avfilter_graph_parse_ptr for ffmpeg
vf_lavfi: copy AVFrame metadata into vf_lavfi priv

store it as mp_tas and add VFCTRL_GET_METADATA to access it from elsewhere

Signed-off-by: wm4 <wm4@nowhere>

old-configure test by wm4.
command: add vf-metadata property

This is a read-only property that uses VFCTRL_GET_METADATA
to retrieve mp_tags metadata from a filter specified by label

Signed-off-by: wm4 <wm4@nowhere>
TOOLS: vf-metadata: lua cropdetect example script

Signed-off-by: wm4 <wm4@nowhere>
af_lavfi: fix graph parse deprecation warning
af_volume: fix clang -Wsometimes-uninitialized
Kill all tabs

I hate tabs.

This replaces all tabs in all source files with spaces. The only
exception is old-makefile. The replacement was made by running the
GNU coreutils "expand" command on every file. Since the replacement was
automatic, it's possible that some formatting was destroyed (but perhaps
only if it was assuming that the end of a tab does not correspond to
aligning the end to multiples of 8 spaces).
Remove radio://

It was disabled by default, works only for analogue radio, and I bet
nobody uses it.