dhcpcd-6.8.2: add ifaddrs.c and ifaddrs.h

Add an Android implementation of ifaddrs to the
dhcpcd-6.8.2 repo, which this daemon depends on.

ifaddr.c cherry-picked from
https://googleplex-android.git.corp.google.com/platform/external/dhcpcd/+/master
at 31db56e5b40726fed587656ac1730705c79741b9.

ifaddr.h cherry-picked from
https://googleplex-android.git.corp.google.com/platform/external/dhcpcd/+/master
at e86eee143ed21592f88a46623a81f71002430459.

BUG: 22956197
Change-Id: Id19c9ee8e7c0c32b36742052f9ee63dc197aa218
2 files changed