ipdb: update `release()` documentation.

Bug-Url: https://github.com/svinota/pyroute2/issues/59
Bug-Url: https://github.com/svinota/pyroute2/issues/83
iproute: support keyword arguments / NLA
ipdb: support broadcast address specification

Bug-Url: https://github.com/svinota/pyroute2/issues/85
Merge pull request #1 from svinota/master

Sync with original