User Defined Structs

[sunjay]

Support basic struct syntax including nested structs:

struct Foo {
    x: u8,
    y: u8,
}

struct Bar {
    pos: Foo,
    data: u8,
}

struct Unit;

Memory layout will likely be sequential though we shouldn't put any guarantees on ordering. This is essentially a way to group variables when passing them around to functions.

• [ ] Be able to use structs where other types used to be used (arrays, functions #16, etc.)
• [ ] Struct names cannot be paths
• [ ] Struct names cannot be keywords