[Implement] ParameterCount

[jtenner]

Usage:

switch(ParameterCount<CallbackType>()) {
  case 1: call_indirect(func, arg0); break;
  case 2: call_indirect(func, arg0, arg1); break;
  case 3: call_indirect(func, arg0, arg1, arg2); break; // etc
}

Useful for EventEmitter.prototype.emit() and EventEmitter.on().

[jtenner]

closed in favor of #739