Added tlv_attr_cmp.
Added hcp subscription stuff (first draft), and changed hcp_node_get_tlvs signature to return tlv_attr (and added some iteration utilities related to that).
Doing break inside do-while wasn't helping. Made ENSURE_VALID bit less pretty but actually working macro.
Moved hex_repr to hcp_i.h
Added bit more thorough test for notifications.
Changed tlv_attr_cmp to be network order (=raw data), and using it also in hcp, and added test suite to make sure it behaves expectedly.