Extend type declarations to include initial value

Extend the type definition block to include an initial value in a declaration. Code examples:

st: declare struct! [
	a		[integer! 99]
	b		[logic! false]
]

If 'FUNCTION proposal accepted:

f: function [
	i		[integer!]
][
	finished?	[logic! false]
	moulded-int	[c-string! "          "]
][
	; function code
]