player: ordered chapters: filter missing chapters

Ever since someone (not me) added some Matroska features which nobody
ever uses (ordered edition or some bullshit), I haven't had a fucking
clue what the fuck is going on in this fucking file. (Still agreed to
it, so it's my fault.)

mplayer2 handled missing chapters correctly (and I suppose in a somewhat
clean/simple manner), but the changed code doesn't. Since I can't even
follow this code because it's so arcanely complicated, just add a hack
that has the same effect.
player: ordered chapters: bullshit reduction

Nobody cares about these redundant messages, they make the code even
more complicated than it has to be, and also they're annoying.
player: ordered chapters: cosmetics

Drop some meaningless comments, fix codingstyle, fix some formatting
victims of the mp_msg refactoring, replace some memcpys with
assignments.
Add Javascript scripting support using MuJS

Almost identical API to the Lua support, except:
- The global mp, mp.msg and mp.utils are always available
- On errors returning undefined and the error is at mp.last_error_string
- Timers are JS "standard" global set/clear Timeout/Interval/Immediate
- Supports CommonJS style module/require
- At mp.utils: read_file (any), and load_file, run_file for js files
- Global print and dump functions
- mp.options currently unsupported

Required Mujs (clone, make, make install):
- http://mujs.com/ - git://git.ghostscript.com/mujs.git
- Mirror - https://github.com/ccxvii/mujs
JS: 'reqire' was broken for scripts
JS: minor cleanups

- Stray printf's
- Remove names from anonymous functions which are unlikely
  to show on stack traces to reduce clutter
javascript: C style cleanups
options: allows javascript also when Lua is not configured
js: replace lua-opts for script-opts
pr1351: simplified file functions
pr1351: cleanups (except for unused/legacy stuff)
pr1351: remove undocumented API which the OSC uses
mu2duk-WIP
mu2duk - seems fully working after few short tests
mu2duk: comments and cleanups. TODO: support either via config
mu2duk: cleanups and refactoring
mu2duk: MUD_WRAPPER now use nargs at runtime
mu2duk: provide js backend info
mu2duk: fix js_Setlength, simplify error print
mu2duk: clearer wrapper with JS_C_FUNC