src: port openBSC over libosmo-abis

This is a big patch that ports openBSC over libosmo-abis.
Sorry, the changes that are included here are all dependent
of libosmo-abis, splitting them into smaller pieces would
leave the repository in some intermediate state, which is
not desired.

The main changes are:

- The directory libabis/ has been removed as it now lives in
  libosmo-abis.

- new configuration file format for nanoBTS and HSL femto, we
  need to define the virtual e1_line and attach it to the OML
  link.

- all the existing BTS drivers (nanoBTS, hsl femto, Nokia site,
  BS11 and rbs2000) now use the new libosmo-abis framework.

- use r232 input driver available in libosmo-abis for bs11_config.

- use ipa_msg_recv instead of old ipaccess_read_msg function.

- delete definition of gsm_e1_subslot and input_signal_data.
  These structures now lives in libosmo-abis.

Most of this patch are deletions of libabis/ which has been
moved to libosmo-abis.

This patch also modifies openBSC to use all the new definitions
available in libosmocore and libosmo-abis. In order to do that,
we have replaced the following:

- DINP, DMI, DMIB and DMUX by their respective DL* correspondences.
- SS_GLOBAL by SS_L_GLOBAL
- SS_INPUT by SS_L_INPUT
- S_GLOBAL_SHUTDOWN by S_L_GLOBAL_SHUTDOWN
- SS_INPUT by SS_L_INPUT
- S_INP_* by S_L_INP_* sub-signals
- E1INP_NODE by L_E1INP_NODE vty node

This patch has been tested with:
- one nanoBTS
- the HSL femto with the examples available under libosmo-abis
- BS11 with both dahdi and misdn drivers.
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c
index 445f459..c42061b 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c
@@ -48,6 +48,7 @@
 #include <osmocom/core/application.h>
 #include <osmocom/core/talloc.h>
 
+#include <osmocom/gsm/tlv.h>
 #include <osmocom/gsm/gsm0808.h>
 #include <osmocom/gsm/protocol/gsm_08_08.h>
 
@@ -57,6 +58,8 @@
 
 #include <osmocom/sccp/sccp.h>
 
+#include <osmocom/abis/ipa.h>
+
 #include "../../bscconfig.h"
 
 #define SCCP_CLOSE_TIME 20
@@ -95,14 +98,14 @@
 static void queue_for_msc(struct bsc_msc_connection *con, struct msgb *msg)
 {
 	if (!con) {
-		LOGP(DINP, LOGL_ERROR, "No MSC Connection assigned. Check your code.\n");
+		LOGP(DLINP, LOGL_ERROR, "No MSC Connection assigned. Check your code.\n");
 		msgb_free(msg);
 		return;
 	}
 
 
 	if (osmo_wqueue_enqueue(&con->write_queue, msg) != 0) {
-		LOGP(DINP, LOGL_ERROR, "Failed to enqueue the write.\n");
+		LOGP(DLINP, LOGL_ERROR, "Failed to enqueue the write.\n");
 		msgb_free(msg);
 	}
 }
@@ -361,13 +364,13 @@
 	struct msgb *msg;
 
 	if (length > 4096 - 128) {
-		LOGP(DINP, LOGL_ERROR, "Can not send message of that size.\n");
+		LOGP(DLINP, LOGL_ERROR, "Can not send message of that size.\n");
 		return;
 	}
 
 	msg = msgb_alloc_headroom(4096, 128, "to-bsc");
 	if (!msg) {
-		LOGP(DINP, LOGL_ERROR, "Failed to allocate memory for BSC msg.\n");
+		LOGP(DLINP, LOGL_ERROR, "Failed to allocate memory for BSC msg.\n");
 		return;
 	}
 
@@ -783,18 +786,19 @@
 
 static int ipaccess_msc_read_cb(struct osmo_fd *bfd)
 {
-	int error;
 	struct bsc_msc_connection *msc_con;
-	struct msgb *msg = ipaccess_read_msg(bfd, &error);
+	struct msgb *msg;
 	struct ipaccess_head *hh;
+	int ret;
 
 	msc_con = (struct bsc_msc_connection *) bfd->data;
 
-	if (!msg) {
-		if (error == 0)
+	ret = ipa_msg_recv(bfd->fd, &msg);
+	if (ret <= 0) {
+		if (ret == 0)
 			LOGP(DNAT, LOGL_FATAL, "The connection the MSC was lost, exiting\n");
 		else
-			LOGP(DNAT, LOGL_ERROR, "Failed to parse ip access message: %d\n", error);
+			LOGP(DNAT, LOGL_ERROR, "Failed to parse ip access message: %d\n", ret);
 
 		bsc_msc_lost(msc_con);
 		return -1;
@@ -1252,21 +1256,22 @@
 
 static int ipaccess_bsc_read_cb(struct osmo_fd *bfd)
 {
-	int error;
 	struct bsc_connection *bsc = bfd->data;
-	struct msgb *msg = ipaccess_read_msg(bfd, &error);
+	struct msgb *msg;
 	struct ipaccess_head *hh;
 	struct ipaccess_head_ext *hh_ext;
+	int ret;
 
-	if (!msg) {
-		if (error == 0)
+	ret = ipa_msg_recv(bfd->fd, &msg);
+	if (ret <= 0) {
+		if (ret == 0)
 			LOGP(DNAT, LOGL_ERROR,
 			     "The connection to the BSC Nr: %d was lost. Cleaning it\n",
 			     bsc->cfg ? bsc->cfg->nr : -1);
 		else
 			LOGP(DNAT, LOGL_ERROR,
 			     "Stream error on BSC Nr: %d. Failed to parse ip access message: %d\n",
-			     bsc->cfg ? bsc->cfg->nr : -1, error);
+			     bsc->cfg ? bsc->cfg->nr : -1, ret);
 
 		bsc_close_connection(bsc);
 		return -1;