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/doc/examples/osmo-bsc/osmo-bsc.cfg b/openbsc/doc/examples/osmo-bsc/osmo-bsc.cfg
index 0a64917..97704fb 100644
--- a/openbsc/doc/examples/osmo-bsc/osmo-bsc.cfg
+++ b/openbsc/doc/examples/osmo-bsc/osmo-bsc.cfg
@@ -39,6 +39,8 @@
 line vty
  no login
 !
+e1_input
+ e1_line 0 driver ipa
 network
  network country code 1
  mobile network code 1
@@ -86,7 +88,7 @@
   rach tx integer 9
   rach max transmission 7
   ip.access unit_id 0 0
-  oml ip.access stream_id 255
+  oml ip.access stream_id 255 line 0
   neighbor-list mode manual-si5
   neighbor-list add arfcn 100
   neighbor-list add arfcn 200