hlr: Export + Declare global g_hlr symbol

It is a global variable, and it's sort of bogus if every C file
re-declares it as a static global variable that is assigned to the
same value as the "real" global one during start-up.

Change-Id: I6f3e50f071fb2fbbe58413b4760dc2215055a444
diff --git a/src/hlr_vty.h b/src/hlr_vty.h
index cd2ff73..bc9c2e5 100644
--- a/src/hlr_vty.h
+++ b/src/hlr_vty.h
@@ -34,4 +34,4 @@
 
 int hlr_vty_is_config_node(struct vty *vty, int node);
 int hlr_vty_go_parent(struct vty *vty);
-void hlr_vty_init(struct hlr *hlr, const struct log_info *cat);
+void hlr_vty_init(const struct log_info *cat);