Add `getGlobals` and `setGlobals` methods on compiled Catspeak functions

[katsaii]

Rendered:

var asg = Catspeak.parseString(@'
  print = function(_str) { 
    show_debug_message(_str); 
  } 
');

var func = Catspeak.compileGML(asg);
func();

var globals = func.getGlobals();
globals.print("Hello World");