dec_sub: don't print sub charset of it's empty
dec_sub: fix memory leak when using subtitle codepage conversion
options: remove -lavdopts debug suboption

This can be set as avopt instead.
options: rename -lavdopts to -vd-lavc, -lavfdopts to -demuxer-lavf

Also change manpage so that top-level options are documented instead
of suboptions. Suboptions still work, but might go away eventually.
options: rename --rawvideo to --demuxer-rawvideo, same with --rawaudio
options: rename --mkv-subtitle-preroll, --dtshd

We still keep the old names as alias for short-time compatibility.
stream: redo memory streams

Make memory streams actual streams. This causes fewer weird corner cases
and actually allows using demuxers with them.
core: rename mplayer.h and quvi.c

mplayer.h used to be used for much more stuff, but all what is left are
quvi related definitions. Rename quvi.c as well to make its purpose
clearer.
core: add libquvi 0.9 support

This adds support for libquvi 0.9.x, and these features:
- start time (part of youtube URL)
- youtube subtitles
- alternative source switching ('l' and 'L' keys)
- youtube playlists

Note that libquvi 0.9 is still in development. Although this seems to
be API stable now, it looks like there will be a 1.0 release, which is
supposed to be the next stable release and the actual successor of
libquvi 0.4.x.
configure: prefer libquvi 0.4.x over libquvi 0.9.x

Because 0.4.x is the current series of stable releases.
vf_rotate: fix params >= 4
mp_image: copy palette only if allocated

Normally, we assume that IMGFMT_PAL8 always has a palette allocated
in plane 1. But there may be corner cases in ffmpeg where it doesn't
(namely pseudo-pal stuff).
video: add a new method to configure filters and VOs

The filter chain and the video ouputs have config() functions. They are
strictly limited to transfering the video size and format. Other
parameters (like color levels) have to be transferred separately.

Improve upon this by introducing a separate set of reconfig() functions,
which use mp_image_params to carry format parameters. This struct
contains all image format related parameters from config(), plus
additional parameters such as colorspace.

Change vf_rotate to use it, as well as vo_opengl. vf_rotate is just
an example/test case, but vo_opengl will need it later.

The intention is also to get rid of VOCTRL_SET_YUV_COLORSPACE. This
information is now handed to the VOs via reconfig(). The getter,
VOCTRL_GET_YUV_COLORSPACE, will still be needed though.
vo_opengl: handle chroma location

Use the video decoder chroma location flags and render chroma locations
other than centered. Until now, we've always used the intuitive and
obvious centered chroma location, but H.264 uses something else.

FFmpeg provides a small overview in libavcodec/avcodec.h:

-----------
/**
 *  X   X      3 4 X      X are luma samples,
 *             1 2        1-6 are possible chroma positions
 *  X   X      5 6 X      0 is undefined/unknown position
 */
enum AVChromaLocation{
    AVCHROMA_LOC_UNSPECIFIED = 0,
    AVCHROMA_LOC_LEFT        = 1, ///< mpeg2/4, h264 default
    AVCHROMA_LOC_CENTER      = 2, ///< mpeg1, jpeg, h263
    AVCHROMA_LOC_TOPLEFT     = 3, ///< DV
    AVCHROMA_LOC_TOP         = 4,
    AVCHROMA_LOC_BOTTOMLEFT  = 5,
    AVCHROMA_LOC_BOTTOM      = 6,
    AVCHROMA_LOC_NB             , ///< Not part of ABI
};
-----------

The visual difference is literally minimal, but since videophiles
apparently consider this detail as quality mark of a video renderer,
support it anyway. We don't bother with chroma locations other than
centered and left, though.

Not sure about correctness, but it's probably ok.
csputils.h: don't recursively include libavcodec header

Some functions (avcol_spc_to_mp_csp() etc.) used libavcodec enum types
as parameters. Remove these in order to get rid of the avcodec.h
include statement. This prevents that avcodec.h is recursively
included by dozens of files. Fix mp_image.c, which used the header
without explicitly including avcodec.h.
cocoa_common: uninit fs window properly

In fullscreen `s->window` is the windowed window. So freeing that didn't get
rid of the FS window and OpenGL view.

Fixes #122
[ci skip]
command: add properties for playlist position

playlist-pos can set/get the current playlist index. playlist-count
returns the number of entries in the playlist.
command: make raw percent-pos property return fractions

percent-pos was an integer (0-100). Sometimes higher precision is
wanted, but the property is this way because fractional parts would
look silly with normal OSD usage. As a compromise, make percent-pos
double (i.e. includes fractional parts), but print it as integer.

So ${percent-pos} is like an integer, but not ${=percent-pos}.
input: handle mouse movement differently

Before this commit, mouse movement events emitted a special command
("set_mouse_pos"), which was specially handled in command.c. This was
once special-cased to the dvdnav and menu code, and did nothing after
libmenu and dvdnav were removed.

Change it so that mouse movement triggers a pseudo-key ("MOUSE_MOVE"),
which then can be bound to an arbitrary command. The mouse position is
now managed in input.c. A command which actually needs the mouse
position can use either mp_input_get_mouse_pos() or mp_get_osd_mouse_pos()
to query it. The former returns raw window-space coordinates, while the
latter returns coordinates transformed to OSD- space. (Both are the same
for most VOs, except vo_xv and vo_x11, which can't render OSD in
window-space. These require extra code for mapping mouse position.)

As of this commit, there is still nothing that uses mouse movement, so
MOUSE_MOVE is mapped to "ignore" to silence warnings when moving the
mouse (much like MOUSE_BTN0).

Extend the concept of input sections. Allow multiple sections to be
active at once, and organize them as stack. Bindings from the top of
the stack are preferred to lower ones.

Each section has a mouse input section associated, inside which mouse
events are associated with the bindings. If the mouse pointer is
outside of a section's mouse area, mouse events will be dispatched to
an input section lower on the stack of active sections. This is intended
for scripting, which is to be added later. Two scripts could occupy
different areas of the screen without conflicting with each other. (If
it turns out that this mechanism is useless, we'll just remove it
again.)
manpage: document input sections