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/include/openbsc/rtp_proxy.h b/openbsc/include/openbsc/rtp_proxy.h
index d128e4f..f82711a 100644
--- a/openbsc/include/openbsc/rtp_proxy.h
+++ b/openbsc/include/openbsc/rtp_proxy.h
@@ -25,8 +25,8 @@
 
 #include <netinet/in.h>
 
-#include <openbsc/linuxlist.h>
-#include <openbsc/select.h>
+#include <osmocore/linuxlist.h>
+#include <osmocore/select.h>
 
 enum rtp_rx_action {
 	RTP_NONE,