STRUCT_MEMBER_ACCESS Add support for using variables inside other variables

[gtker]

In the Wrath MovementBlock the first few fields are identical to the fields of the MovementInfo.

Emulators send an actual MovementInfo but we have to duplicate the fields because we can't reach into the structs.

We want to be able to do

flag A : u8 {
	ONE = 1;
	TWO = 2;
}
flag B : u8 {
	FOUR = 4;
	EIGHT = 8;
}

struct T {
	A a;
}
struct Y {
	T t;
	if (t.a & ONE) {
		u8 one;
	}
}

It is not certain what the generated Rust could should look like.

[gtker]

The motivation for doing this was partly automatically converting to/from MovementInfo and the resulting type that contained a MovementInfo, but this would introduce a very nasty edge case that would only be used for a single thing. Manually writing a conversion function is simpler.