Merge pull request #3408 from bluca/relicense

Problem: missing relicensing statement from bluca

RELICENSE/bluca.md

+# Permission to Relicense under MPLv2 or any other OSI approved license chosen by the current ZeroMQ BDFL
+
+This is a statement by Luca Boccassi (bluca)
+that grants permission to relicense his copyrights in the libzmq C++
+library (ZeroMQ) under the Mozilla Public License v2 (MPLv2) or any other
+Open Source Initiative approved license chosen by the current ZeroMQ
+BDFL (Benevolent Dictator for Life).
+
+A portion of the commits made by the Github handle "bluca", with
+commit author "Luca Boccassi <luca.boccassi@gmail.com>" or
+"Luca Boccassi <bluca@debian.org>", are copyright of Luca Boccassi.
+This document hereby grants the libzmq project team to relicense libzmq,
+including all past, present and future contributions of the author listed
+above.
+
+Luca Boccassi
+2019/02/16