signal: use namespace prefix osmo_signal*

Summary of changes:

s/signal_cbfn/osmo_signal_cbfn/g
s/register_signal_handler/osmo_signal_register_handler/g
s/unregister_signal_handler/osmo_signal_unregister_handler/g
s/dispatch_signal/osmo_signal_dispatch/g
diff --git a/include/osmocom/core/signal.h b/include/osmocom/core/signal.h
index 02d83d2..535fd18 100644
--- a/include/osmocom/core/signal.h
+++ b/include/osmocom/core/signal.h
@@ -1,15 +1,14 @@
-#ifndef OSMOCORE_SIGNAL_H
-#define OSMOCORE_SIGNAL_H
+#ifndef OSMO_SIGNAL_H
+#define OSMO_SIGNAL_H
 
-typedef int signal_cbfn(unsigned int subsys, unsigned int signal,
-			void *handler_data, void *signal_data);
+typedef int osmo_signal_cbfn(unsigned int subsys, unsigned int signal, void *handler_data, void *signal_data);
 
 
 /* Management */
-int register_signal_handler(unsigned int subsys, signal_cbfn *cbfn, void *data);
-void unregister_signal_handler(unsigned int subsys, signal_cbfn *cbfn, void *data);
+int osmo_signal_register_handler(unsigned int subsys, osmo_signal_cbfn *cbfn, void *data);
+void osmo_signal_unregister_handler(unsigned int subsys, osmo_signal_cbfn *cbfn, void *data);
 
 /* Dispatch */
-void dispatch_signal(unsigned int subsys, unsigned int signal, void *signal_data);
+void osmo_signal_dispatch(unsigned int subsys, unsigned int signal, void *signal_data);
 
-#endif /* OSMOCORE_SIGNAL_H */
+#endif /* OSMO_SIGNAL_H */