This is actually for the new change I'm working on, but let's retrofit
it first to separate any bugs in these changes from those in the new
change...
Test: treehugger
Change-Id: I890aeb61f9792810a77ad0da3f9674c9cc5db7bb
This is just a subset of the recently-implemented getifaddrs(3), though if
we want to handle interfaces (such as "rmnet_*") that don't have an address,
we need to either expose ifaddrs_storage and keep track of which interfaces
we've already seen (which is pretty messy), or refactor the netlink code so
we can reuse it and just extract the information we need for if_nameindex(3).
This patch goes the latter route.
Also clean up if_nametoindex(3) and if_indextoname(3).
Change-Id: I5ffc5df0bab62286cdda2e7af06f032c767119a8
