split 'libosmocore' from openbsc codebase

This library is intended to collect all generic/common funcitionality
of all Osmocom.org projects, including OpenBSC but also OsmocomBB

The library currently includes the following modules:

bitvec, comp128, gsm_utils, msgb, select, signal, statistics, talloc, timer,
tlv_parse, linuxlist

msgb allocation error debugging had to be temporarily disabled as it depends on
'debug.c' functionality which at the moment remains in OpenBSC
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 10ebd6d..aebd02c 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -30,12 +30,12 @@
 
 #include <openbsc/gsm_data.h>
 #include <openbsc/gsm_04_08.h>
-#include <openbsc/gsm_utils.h>
+#include <osmocore/gsm_utils.h>
 #include <openbsc/abis_rsl.h>
 #include <openbsc/chan_alloc.h>
 #include <openbsc/bsc_rll.h>
 #include <openbsc/debug.h>
-#include <openbsc/tlv.h>
+#include <osmocore/tlv.h>
 #include <openbsc/paging.h>
 #include <openbsc/signal.h>
 #include <openbsc/meas_rep.h>