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/rtp_proxy.c b/openbsc/src/rtp_proxy.c
index 83b774f..9b1f4d9 100644
--- a/openbsc/src/rtp_proxy.c
+++ b/openbsc/src/rtp_proxy.c
@@ -29,10 +29,10 @@
 #include <time.h>        /* clock() */
 #include <sys/utsname.h> /* uname() */
 
-#include <openbsc/talloc.h>
+#include <osmocore/talloc.h>
 #include <openbsc/gsm_data.h>
-#include <openbsc/msgb.h>
-#include <openbsc/select.h>
+#include <osmocore/msgb.h>
+#include <osmocore/select.h>
 #include <openbsc/debug.h>
 #include <openbsc/rtp_proxy.h>