Log Message:
libnice: update to 0.1.15.

libnice 0.1.15 (2018-12-27)
===========================
Add support for Regular Nomination
Removal of the global lock over all agents
Add method to compare candidate targets
Added optional Meson build system, future releases will remove autotools
Renamed all members of PseudoTcpState enum (compile-time API change)
Now drops all packets from addresses that have not been validated by an ICE check
Multiple improvements to ICE interoperability
Improved RFC compliance
Improved OC2007 compatibility mode alternate-server support