Added call to register 'intercepted' method

[desertkun]

Often you already have some code base you would like to introduce into Javascript world. But the API you have is just not ready to be used in dukglue_register_method:

• It's not recommended to edit the existing code base
• Some methods return 'by value'
• Magic enums are used javascript have no idea about
• Arguments are const references

You can try to wrap your object into a wrapper that would add that dukglue-ready methods, but sometimes even that is just not possible.

Say you have this class:

class A {
public:
    B process(const C& c, Vector2 v);
};

Then using simple wrapper that does not touch the original class:

namespace AWrapper {
    B* process(A* instance, duk_context* context, C* c, Vector2* v) {
        static B b;
        b = instance->process(*c, *v);
        return &b;
    }
};

You can bind it:

dukglue_register_intercepted_method<A>(ctx, "process", &AWrapper::process);

The bound should have two additional arguments added before the args that javascript may pass:

1. A pointer to current class instance
2. A pointer to current context

Under the hood it behaves like dukglue_register_method and dukglue_register_function combined, since both obj_ptr and func_ptr are used (honestly have no idea how it works there are way to many template magic up there).

I would appreciate a comment on how to make this PR possible.