allow javascript generator to work with both node and browser

[tridge]

This builds on the work by @IamPete1 in #995 and gets the generated javascript to pass tests, plus work in both a browser and in command line node tools

example usage: ArduPilot/WebTools#265

also adds wss support to mavutil.py, so mavproxy can use wss: connections

[tridge]

@Huibean could you test this with your browser efforts?

[Huibean]

@tridge I just have a try using mavlink.js generated in this pr, the program freeze up every time after connect websocket/webserial, something wrong inside mavlinkProcessor.send, tomorrow will digging into it

[tridge]

something wrong inside mavlinkProcessor.send, tomorrow will digging into it

ok, thanks!

[Huibean]

@tridge there is a dead loop here

[tridge]

there is a dead loop here

does it keep getting messages?

[Huibean]

there is a dead loop here

does it keep getting messages?

function just called once, I set a breakpoint there once enter while never return, then memory leak and crash

[Huibean]

runtime error logs is going into the parse buffer, I temporary fix it by checking BAD_DATA, now I will fix the "Unpack" import error and continue

MAVLink20Processor.prototype.parseBuffer = function(s) {

    // Get a message, if one is available in the stream.
    var m = this.parseChar(s);

    // No messages available, bail.
    if ( null === m ) {
        return null;
    }

    // While more valid messages can be read from the existing buffer, add
    // them to the array of new messages and return them.
    var ret = [];
    ret.push(m);
    while(true) {
        m = this.parseChar(null);
        if ( null === m || m._id === mavlink20.MAVLINK_MSG_ID_BAD_DATA) {
            // No more messages left.
            return ret;
        }
        ret.push(m);
    }

}

[tridge]

discussed with @Huibean, working now