This came up while fixing 'make distcheck'; this is certainly not the easiest
way but it makes sense to have the headers in include/, like we do in openbsc.
The easy alternative might be to add -I$(top_srcdir)/src to src/Makefile.am.
Remove -I$(top_srcdir)/src from src/tests/Makefile.am, no longer needed.
Change-Id: I5a82e029dcdc4df0a60a31271a4883393fe59234
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