Fix some style and naming stuff; make Jack::Client "wrap" a jack_client_t* pointer
Make the Jack::Client use the wrapped pointer instead of @ptr ivar
Give PassThruNode special constructor and ensure it is called by setting the ruby alloc function
Define macro NODE_W_ALLOC to make child class definitions easier
Make the NODE_W_ALLOC definition itself a little dryer using preprocessor token concatenation magic
Further generalize aforementioned macro to generate all 4 _w_ functions
Move CPP2RB macro definitions to util/cpp2rb.hpp