build: fix unicode handling of the version string

Don't pass unicode types to waf ENV.
As per https://code.google.com/p/waf/issues/detail?id=1420
This directly fixes the "CFVersion" key in the .app bundle plist.
af_volume: remove double-negated suboption

You had to use "no-replaygain-noclip" to set this option. Rename it, so
that only one negation is needed.
manpage: af: minor syntax improvements
af_volume: separate softvol volume control from replaygain level

Currently, both replaygain adjustment and user volume control (if
softvol is enabled) share the same variable. Sharing the variable would
cause especially if --volume is used; then the replaygain volume would
always be overwritten.

Now both gain values are simple added right before doing filtering.
af_volume: add detach option

Maybe this should be default. On the other hand, this filter does
something even if the volume is neutral: it clips samples against the
allowed range, should the decoder or a previous filter output garbage.
af_volume: don't print missing replaygain tags as error

There's no reason to. Audio files often lack them.
ao: print (estimated) device buffer size on init in verbose mode
stream_dvdnav: implement STREAM_CTRL_GET_NUM_TITLES for dvdnav

This commit provides impelmentation of STREAM_CTRL_GET_NUM_TITLES
for dvdnav stream. Other streams for DVD or Blu-ray are already
provide STREAM_CTRL_GET_NUM_TITLES.
command: add new property 'title'

This commit adds new property 'title' which indicates current
playing title of disc. This property is useful when using a stream
whose title can be changed during playback, e.g., dvdnav.
command: prefix DVD title properties with "dvd-"

They're strictly DVD-only, so it's better to mark them as such. This
also documentes the "title" (now renamed to "dvd-title") property.

This also avoids collision with the --title option. (Technically, there
was no problem. But it might be confusing for users, since we have a
policy of naming properties and options the same if they refer to the
same underlying functionality.)
options: fix off-by-1 error in option help output
DOCS/coding-style: add another requirement for commit messages
command: rename dvd- properties to disc-

Since these are not DVD-only, but can also be used with BDs.
demux_libass: change how external ASS subtitles are loaded

Instead of parsing the ASS file in demux_libass.c and trying to pass the
ASS_Track to the subtitle renderer, just read all file data in
demux_libass.c, and let the subtitle renderer pass the file contents to
ass_process_codec_private(). (This happens to parse full files too.)

Makes the code simpler, though it also relies harder on the (messy)
probe logic in demux_libass.c.
vd_lavc: ridiculous workaround for Libav 9 compatibility

This "sometimes" crashed when seeking. The fault apparently lies in
libavcodec: the decoder returns an unreferenced frame! This is
completely insane, but somehow I'm apparently still expected to
work this around. As a reaction, I will drop Libav 9 support in the
next commit. (While this commit will go into release/0.3.)
build: drop support for Libav 9

I have no tolerance for this garbage anymore. There are tons of issues
with it (see e.g. previous commit), and there is no reason to use it
either. Use Libav git, or Libav 10 when it's released.

This also drops support for earlier FFmpeg release, which have exactly
the same issues as Libav 9. FFmpeg 2.1.4 is still supported, because
it's the latest release, and is reasonably recent. (Although this will
probably also be dropped as soon as FFmpeg 2.2 is released.)

Assumed version table (lots of nonsensical numbers):

        FFmpeg 2.1.4    FFmpeg (n2.2-rc2)   Libav (v10_beta2)

lavu    52.48.101       52.66.100           53.3.0
lavc    55.39.101       55.52.102           55.34.1
lavf    55.19.104       55.33.100           55.12.0
lsws    2.5.101         2.5.101             2.1.2
lavi    3.90.100        4.2.100             4.2.0
lswr    0.17.104        0.18.100            -
lavr    1.1.0           1.2.0               1.1.0

libpostproc and libavdevice are not interesting.

Following this commit, code needed just to support old Libav versions
will start to be removed.
travis-ci: update ffmpeg stable tarball
vd_lavc: remove compatibility crap

All this code was needed for compatibility with very old libavcodec
versions only (such as Libav 9).

Includes some now-possible simplifications too.
sub: remove old MPlayer DVD sub decoder

The DVD sub decoder in Libav 9 was broken/incomplete, so we kept the
MPlayer decoder around. Now it's not needed anymore.
af_lavrresample: remove avresample_set_channel_mapping() fallbacks

This function is now always available.

Also remove includes of reorder_ch.h from some AOs (these are just old
relicts).