* Many parser improvements!

1. Has been added support for parameter default values on function declaration:

   Example:
	func hello (name="Sidef") {
            say name;
	};
	hello();          # prints: "Sidef"
	hello("World");   # prints: "World"

   * the default value is evaluated at compile-time
   * the value can be any expression you like, but make sure to put it inside parentheses

2. Improved the declaration of 'var'iables, 'const'ants and 'static' variables:

   Example:
	var (x, y=755, z=777) = (666, 655);
	say x;    # prints: 666
	say y;    # prints: 655
	say z;    # prints: 777