Allow giving names to function parameters

[ISSOtm]

Currently, I have to do things like

	def ret();
	def yld();
	def jmp(u16 /* addr */);
	def put_u8(u8 /* var_id */, u8 /* value */);
	def move_obj(u8 /* id */, u8 /* x */, u8 /* y */);

to remember what parameter is what, which looks a little bleh. I think it'd be better to allow optional (and ignored!) names for the parameters. Syntax highlighting could be improved even better from it, I think!

[evie-calico]

This is a good suggestion but i'll probably go with the rust syntax (name: type) rather than C's (type name).

[evie-calico]

I just realized that you probably suggested that because variable declarations are the same as C and now that I'm thinking about it I'd prefer a let var: type too.

[ISSOtm]

All of those are fine by me.