RFC 3978 Update to Recognize the IETF Trust

This document updates RFC 3978 "IETF Rights in Contributions" to recognize that the IETF Trust is now the proper custodian of all IETF-related intellectual property rights. This document does not constrain how the IETF Trust exercises those rights. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.