cocoa_common: fix crash with dead key input and simplify related code

Fixes #29. When a user used dead input keys (like the accent key), `mpv`
crashed because the code tried to access the 0 element of a characters array
(which was empty).

While I was closing this bug, I refactored some related conditionals to
make the code more readable.
mplayer: don't display "-1" as chapter when chapter seek fails

Increase robustness against out of bound chapter numbers. Normally
these functions expect that the callers sanitize the chapter number.
This went wrong at least in add_seek_osd_messages() (which displayed
a chapter "-1" when chapters were not available). Make these functions
a bit friendler and add some reasonable checks and fallbacks, which
fixes the mentioned chapter seeking case as well.
osd: prevent osd bar from sticking around on seeks

This was supposed to be fixed in f897138, but there's another corner
case. Basically, set_osd_function() reset the OSD time, which is not
nice at all and breaks the logic of letting OSD elements disappear when
they're not wanted anymore. Fix this by adding a separate timer for
this.

Additionally, make sure the OSD bar is _really_ always updated when
visible. Also, redraw the OSD only if the OSD bar actually changes to
prevent redrawing too often (every vo_osd_changed() will flag that the
OSD should be redrawn, even if nothing changes).
options: parse C-style escapes for some options

Being able to insert newline characters ("\n") is useful for
--osd-status-msg, and possibly also for anything that prints to the
terminal. Espcially --term-osd-esc looks relatively useless without
being able to specify escapes.

Maybe parsing escapes should happen during command line / config parsing
instead (for all options).
vd_lavc: fix software decoding fallback

The string is deallocated by the callee after initialization, so
fallback at runtime passes a deallocated string to libavcodec, which
results in random crashes. Regression introduced by commit 4d016a9.
x11_common: uncrustify

Also some other cosmetic changes. And reformat the two remaining doxygen
comments.

Removing MSGLEN in x11_errorhandler() is technically not just a cosmetic
change, but the result is the same anyway.
core: move `xineramascreen` to `MPOpts` as `vo_screen_id`

This is a small cleanup in preparation for the next commit.
core: add fs-screen option for fullscreen display selection

`--fs-screen` allows to decide what display to go fullscreen into. The
semantics of `--screen` changed and now it is only used to select the windowed
display when starting the application.

This is useful for people using mpv with an external TV. They will start
windowed on their laptop's screen and switch to fullscreen on the TV.

@wm4 worked on the x11 and w32 parts of the code. All is squashed in one
commit for history clarity.
options: drop --opt:subopt option names

For all suboptions, "flat" options were available by separating the
parent option and the sub option with ":", e.g. "--rawvideo:w=123". Drop
this syntax and use "-" as separator. This means even suboptions are
available as normal options now, e.g. "--rawvideo-w=123". The old syntax
doesn't work anymore.

Note that this is completely separate from actual suboptions. For
example, "-rawvideo w=123:h=123" still works. (Not that this syntax is
worth supporting, but it's needed anyway, for for other things like vf
and vo suboptions.)

As a consequence of this change, we also have to add new "no-" prefixed
options for flag suboptions, so that "--no-input-default-bindings"
works. ("--input-no-default-bindings" also works as a consequence of
allowing "-input no-default-bindings" - they are handled by the same
underlying option.)

For --input, always use the full syntax in the manpage. There exist
suboptions other than --input (like --tv, --rawvideo, etc.), but since
they might be handled differently in the future, don't touch these yet.

M_OPT_PREFIXED becomes the default, so remove it. As a minor unrelated
cleanup, get rid of M_OPT_MERGE too and use the OPT_SUBSTRUCT() macro in
some places.

Unrelated: remove the duplicated --tv:buffersize option, fix a typo in
changes.rst.
options: fix --no-shuffle and --no-{

--no-shuffle accidentally did nothing after commit 57879a2. The options
--no-{ and --no-} make no sense and shouldn't exist (wrong option type).
demux_rawvideo: remove ancient video dimension presets

I can't see much value in them. Just specify the size manually.
vf_stereo3d: get rid of m_obj_presets_t usage

The code becomes amazingly simpler.
vf_scale: remove video dimension presets ("presize" suboption)

This wasn't really useful, and the option preset mechanism is awfully
complex.
m_option: remove preset mechanism

Was very complicated to use, and its uses have been removed in the
previous commits.

(While this feature sounded kind of useful, it could be rewritten in
a much simpler way, like storing presets as strings, and then using
the option parser to apply a preset. The removed code did some major
pointer juggling to handle raw values, which made it hard to use.)
vf_yadif: switch to option parser, allow disabling by default

Use the option parser instead of sscanf. Remove the parameter changing
the field dominance (it has been marked deprecated for ages). Add a new
suboption "enabled", which can be used to disable the filter by default,
until it's enabled at runtime:

    mpv -vf yadif=enabled=no
vo_direct3d: always clear window before drawing video

This fixes the issue that black borders (e.g. on fullscreen) are not
redrawn, even if OSD rendering changes these areas.

In theory, the code could try some clever things to determine whether
clearing the window is really necessary, but that's probably not worth
the trouble and won't bring any significant performance gain, or might
even make things slower (because the GPU can't discard the old
contents).

Also fix redrawing when changing panscan with OSD disabled.
core: print correct quit message when quitting, simplify code

"End of file" was printed to the terminal instead of "Quit" when exiting
with the "quit" slave command (closing the window and such). Note that
it will still print EOF when it exists because the end of the playlist
is reached.

Do some other (not strictly related) simplifications.
vo_caca: remove OSD support

Recent changes to the OSD code made vo_caca crash when showing OSD.
Since this is a joke VO (== I'd rather not waste my time with it),
remove the OSD support. It wasn't that great anyway.
demux_mf: map to codecs directly

Instead of going through FourCCs and codec_tags.c.
demux_rawvideo: allow setting video codec

Can be used to decode some obscure image formats and similar stuff.