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/libosmocore/include/Makefile.am b/libosmocore/include/Makefile.am
new file mode 100644
index 0000000..f0015d5
--- /dev/null
+++ b/libosmocore/include/Makefile.am
@@ -0,0 +1 @@
+SUBDIRS = osmocore