[BSC] Move the BTS-type specific code from bcs_init.c to bts_*.c

bsc_init.c was a big mess even only for two supported BTS models,
so before adding more BTS types, this needs a cleanup.

All the BTS specific code from bsc_init.c has now moved into
bts_{siemens_bs11,ipaccess_nanobts}.c

This has required that input_event() and nm_state_event() get both
converted to proper libosmocore signals instead of referencing external
symbols.
diff --git a/openbsc/src/input/dahdi.c b/openbsc/src/input/dahdi.c
index 06d9171..934761f 100644
--- a/openbsc/src/input/dahdi.c
+++ b/openbsc/src/input/dahdi.c
@@ -47,6 +47,7 @@
 #include <openbsc/abis_rsl.h>
 #include <openbsc/subchan_demux.h>
 #include <openbsc/e1_input.h>
+#include <openbsc/signal.h>
 #include <osmocore/talloc.h>
 
 #include "lapd.h"
@@ -94,11 +95,11 @@
 		break;
 	case LAPD_MPH_ACTIVATE_IND:
 		DEBUGP(DMI, "MPH_ACTIVATE_IND: sapi(%d) tei(%d)\n", sapi, tei);
-		ret = e1inp_event(e1i_ts, EVT_E1_TEI_UP, tei, sapi);
+		ret = e1inp_event(e1i_ts, S_INP_TEI_UP, tei, sapi);
 		break;
 	case LAPD_MPH_DEACTIVATE_IND:
 		DEBUGP(DMI, "MPH_DEACTIVATE_IND: sapi(%d) tei(%d)\n", sapi, tei);
-		ret = e1inp_event(e1i_ts, EVT_E1_TEI_DN, tei, sapi);
+		ret = e1inp_event(e1i_ts, S_INP_TEI_DN, tei, sapi);
 		break;
 	case LAPD_DL_DATA_IND:
 	case LAPD_DL_UNITDATA_IND: