Lua bindings for sound functions

Just add Lua wrappers for existing MWScript API.

Note that MWSE-Lua has a similar API, but it also has events (addSound/addTempSound/soundObjectPlay) to detect when sounds are about to be played.

API usage examples:

local core = require('openmw.core');
local ambient = require('openmw.ambient');

-- Play a 3D sound with given parameters
local params = {
    timeOffset=0.1
    volume=0.3, 
    loop=false, 
    pitch=1.0
};
core.sound.playSound3d("shock bolt", target, params)
-- Play a 2D sound with given parameters
local params = {
    timeOffset=0.1
    volume=0.3, 
    scale=false, 
    pitch=1.0
};
ambient.playSound("shock bolt", params)
-- Check if given sound is playing
local isPlaying = core.sound.isSoundPlaying("shock bolt", target);
-- Stop sound
core.sound.stopSound("shock bolt", target);
-- Make target to say a voiced line. Lips movement will be used if available.
core.sound.say(target, "Sound\\Vo\\Misc\\tr_almgreet1.mp3", "Many Blessings upon you, my loyal servant.")
-- Make target to say a voiced line. Lips movement will be used if available. Also print a message box even if subtitles are disabled
core.sound.say(target, "Sound\\Vo\\Misc\\tr_almgreet1.mp3", "Many Blessings upon you, my loyal servant.", true)
-- The same, but without speaker
core.sound.say("Sound\\Vo\\Misc\\tr_almgreet1.mp3", "Many Blessings upon you, my loyal servant.", true)
-- Check if given objects says something
local active = core.sound.isSayActive(target);
-- Make target to shut up
core.sound.stopSay(target)
-- Play a 3D sound with given parameters
local params = {
    timeOffset=0.1, 
    volume=0.3, 
    loop=false, 
    pitch=1.0
};
core.sound.playSoundFile3d("Sound\\Vo\\Misc\\tr_almgreet1.mp3", target, params)
-- Play a 2D sound file with given parameters
local params = {
    timeOffset=0.1
    volume=0.3, 
    scale=false, 
    pitch=1.0
};
ambient.playSoundFile("Sound\\Vo\\Misc\\tr_almgreet1.mp3", params)
-- Check if given sound is playing
local isPlaying = core.sound.isSoundFilePlaying("Sound\\Vo\\Misc\\tr_almgreet1.mp3", target);
-- Stop sound
core.sound.stopFileSound("Sound\\Vo\\Misc\\tr_almgreet1.mp3", target);

New functions do not seem to require delayed actions - sound system uses queues, and animation update based on "say" state happens in the main thread when we run animations.

Any suggestions are welcome.