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
Allow Iu Release Command decoding and freeing.
Add Paging decoding and freeing.
These are all needed by hnb-test, which still uses the CN parsing functions,
still to be fixed, as commented in the code.
Add the Security Mode Command procedure code to cn_ranap_rx_initiating_msg_co()
and cn_ranap_free_initiating_msg_co(), for hnb-test (see comments in the code).