Add global HLR struct

Introduce g_hlr of type 'struct hlr' which holds pointers to all
globally accessible variables.

Change-Id: I275d3d54482f696e3378606b2406c7e0ad939e0f
Related: OS#1645
diff --git a/src/Makefile.am b/src/Makefile.am
index 56a5670..1791343 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -14,6 +14,7 @@
 noinst_HEADERS = \
 	auc.h \
 	db.h \
+	hlr.h \
 	luop.h \
 	gsup_router.h \
 	gsup_server.h \