Rename internal classes to avoid conflict with redefinitions

[amieleg]

Angry compiler noises when there's no class in front of a member definition with the same name. Code should not look like this:

class foo {
    public:
    class position position;
}

but should instead look like this:

class foo {
    public:
    [new class name here] position;
}

[lonkaars]

Fixed in #12