[build] Make a number of static libraries build with -fvisibility=hidden ZX-1895 #comment Test: CQ Change-Id: Id3252fcb1de5a6f6e1897da86fba92e2be9d0319
[mdns] Add beginnings of mDNS lib. * Includes a single test to prove the library builds / passes ZX-1719 Change-Id: I333136ad3f18b2a489c016a9a43e06415ca17018