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
Neels Hofmeyr