Basically copy-paste the Iuh local-ip and local-port code to provide
parameterization of the IuCS and IuPS remote addresses.
Add IUCS and IUPS nodes, enhance go_parent_cb and config writing accordingly.
Change-Id: I2c28977011009df4e1fa472290bbbc359e406971
Add include/osmocom/iuh/ named after this project (osmo-iuh), and add vty.h to
define VTY node enum values. Also add (to) Makefile.am and configure.ac to
include in the build.
An upcoming commit will add the actual first config item to the hnbgw/iuh node.
Change-Id: I71545823d3bd81cb888c85df8e298a56c98bf131