Bundles: Serialization conforms to OSC Spec

- No extra padding is required, though it is still accepted for bundles.
- Additional length parameters added to API
- test added to verify extra NULL bytes are not used and the code fails
  predictably when using the wrong length
- This commit should be the end of backwards compatibility breaks in the API
  presented in rtosc.h (in theory this should be equivalent to the
  compatibility of librtosc (aka the C layer))