[Vala] Support for coroutines in Vala

[Serge Hulne <serge hulne gmail com>]

Support for coroutines in Vala:

Has it been dropped ?

otherwise how does one compile examples like:


/////

void foo () yields {

        message ("hello");
        yield;
        message ("world");
}

void main () {
        foo.begin ();
        message ("vala");
        
        var loop = new MainLoop (null, false);
        loop.run ();
}

/////