video, audio: use lavc decoders without codecs.conf entries

Add support for using libavcodec decoders that do not have entries in
codecs.conf. This is currently only used with demux_lavf, and the
codec selection is based on codec_id returned by libavformat. Also
modify codec-related terminal output somewhat to make it use
information from libavcodec and avoid excessively long default output.

The new any-lavc-codec support is implemented with codecs.conf entries
that invoke vd_ffmpeg/ad_ffmpeg without directly specifying any
libavcodec codec name. In this mode, the decoders now instead select
the libavcodec codec based on codec_id previously set by demux_lavf
(if any). These new "generic" codecs.conf entries specify "status
buggy", so that they're tried after any specific entries with
higher-priority status.

Add new directive "anyinput" to codecs.conf syntax. This means the
entry will always match regardless of fourcc. This is used for the
above new codecs.conf entries (so the driver always gets to decide
whether to accept the input, and will fail init() if it can't find a
suitable codec in libavcodec). Remove parsing support for the obsolete
codecs.conf directive "cpuflags". This directive has not had any
effect and has not been used in default codecs.conf since many years
ago.

Shorten codec-related terminal output. When using libavcodec decoders,
show the libavcodec long_name field rather than codecs.conf "info"
field as the name of the codec. Stop showing the codecs.conf entry
name and "vfm/afm" name by default, as these are rarely needed;
they're now in verbose output only. Show "VIDEO:" line at VO
initialization rather than at demuxer open. This didn't really belong
in demuxer code; the new location may show more accurate values (known
after decoder has been opened) and works right if video track is
changed after initial demuxer open.

The vd.c changes (primarily done for terminal output changes) remove
round-to-even behavior from code setting dimensions based on aspect
ratio. I hope nothing depended on this; at least the even values were
not consistently guaranteed anyway, as the rounding code did not run
if the video file did not specify a nonzero aspect value.
demux, vd_ffmpeg: fix demux keyframe flag, set AV_PKT_FLAG_KEY

There was some confusion about the "flags" field in demuxer packets.
Demuxers set it to either 1 or 0x10 to indicate a keyframe (and the
field was not used to indicate anything else). This didn't cause
visible problems because nothing read the value. Replace the "flags"
field with a boolean "keyframe" field. Set AV_PKT_FLAG_KEY based on
this field in packets fed to libavcodec video decoders (looks like PNG
and ZeroCodec are the only ones which depend on values from demuxer;
previously this was hardcoded to true for PNG).

Make demux_mf set the keyframe field in every packet. This matters for
PNG files now that the demuxer flag is forwarded to libavcodec.

Fix logic setting the field in demux_mkv. It had probably not been
updated when adding SimpleBlock support. This probably makes no
difference for any current practical use.
vd_vfw.c: fix part missing from previous commit

vd_vfw.c was missing a change to rename field used from 'flags' to
'keyframe'. This broke compilation with 32-bit Windows codec support
enabled.
demux_lavf: use lavf for RealMedia (.rm) files by default

RealMedia was listed as a format for which the internal demuxer
(demux_real) was preferred over lavf. The original reason for this
(lavf failing to give any timing information for some video frames)
has been fixed in libavformat since. Make demux_lavf the preferred
demuxer for RealMedia.

The libavformat demuxer does still have issues. COOK audio initially
misbehaves after a seek (inconsistent timestamps, audio remaining from
the before-seek position). However, the internal demuxer seemed to be
_consistently_ out of sync with a test file. I haven't done thorough
testing, but the internal demuxer does not seem less buggy.
options: support "no-foo" syntax for flag suboptions

Allow using "no-foo" as an alternative to "foo=no" for flag
suboptions, similarly to what top-level flag options already support.
This means things like "--lavdopts=no-fast" or
"--vo=vdpau:no-chroma-deint" are now supported.
vo_vdpau: disable refresh-aware frame timing when composited

Under a compositing window manager the current VDPAU implementation
behaves differently than without it. Frame flip timing info becomes
incorrect (I guess it only reflects when the frame was sent to the
compositor, not when it was actually shown), and there is no
limitation to at most one frame switch per refresh like without
compositing. Detect whether a compositing window manager is active and
disable refresh-aware frame timing and dropping in this case,
similarly to what fps=-1 would do. This behavior can be controlled
with the new suboption "composite-detect".

Disabling the refresh-aware logic makes timing somewhat less accurate.
Because the video switch rate limit isn't there, the lack of frame
dropping on player side does not impose a hard limit on video FPS, but
does reduce performance somewhat as redundant frames are drawn in
memory.

The existence of a compositing window manager does not guarantee that
the current window is actually composited, so the current check is not
foolproof. In particular, some WMs have support for a "unredirect
fullscreen windows" option. Support for such things could be improved.
demux_rawdv.c: fix change missing from recent 8079f4ff821

Like vd_vfw.c fixed earlier, demux_rawdv.c was also missing a change
needed for the "flags"->"keyframe" demux packet field rename. This
broke compilation with libdv enabled.

Hopefully there aren't more cases. It's hard to reliably check for
references in files that aren't compiled in the local tree if they use
different base variable names, as the "flags" name itself is used for
many unrelated things.
vo_corevideo, vo_sharedbuffer: put private state in vo->priv

These VOs were already using a struct for all private data but the
struct variable itself was static. Change them to store the address in
vo->priv. Also change them to use the new automatic private data
allocation and option parsing mechanism.
vo_sharedbuffer: remove from autoprobe list

This video output is headless and only intended to work with GUIs
explicitly asking for it. This makes it useless to have it in the
autoprobe list.