move headers to include/osmocom/hlr

Apply the same headers structure that we keep in most Osmocom source trees:
Keep noinst_HEADERS in include/osmocom/hlr and include them using
  #include <osmocom/hlr/*.h>

The only header kept in src/ is db_bootstrap.h, because it is generated during
build time. If it was built in include/osmocom/hlr, we would need db.o to
depend on db_bootstrap.h in a different subdir, which automake can't do well.

Change-Id: Ic912fe27f545b85443c5fb713d8c3c8aac23c9ad
diff --git a/src/gsup_server.c b/src/gsup_server.c
index e75bbd7..bee6aef 100644
--- a/src/gsup_server.c
+++ b/src/gsup_server.c
@@ -27,8 +27,8 @@
 #include <osmocom/gsm/gsm48_ie.h>
 #include <osmocom/gsm/apn.h>
 
-#include "gsup_server.h"
-#include "gsup_router.h"
+#include <osmocom/hlr/gsup_server.h>
+#include <osmocom/hlr/gsup_router.h>
 
 static void osmo_gsup_server_send(struct osmo_gsup_conn *conn,
 			     int proto_ext, struct msgb *msg_tx)