bsc: Add vty command to send location trap through VTY

I have manually tested this by entering the VTY command and
observing the CTRL interface using wireshark.

Ticket: OW#1129
diff --git a/openbsc/include/openbsc/osmo_bsc.h b/openbsc/include/openbsc/osmo_bsc.h
index 1032daa..7e931c8 100644
--- a/openbsc/include/openbsc/osmo_bsc.h
+++ b/openbsc/include/openbsc/osmo_bsc.h
@@ -55,4 +55,6 @@
 
 int bsc_ctrl_cmds_install();
 
+void bsc_gen_location_state_trap(struct gsm_bts *bts);
+
 #endif