initial commit of libosmo-abis

still many things to get fixed
diff --git a/include/osmocom/gsm/abis/Makefile.am b/include/osmocom/gsm/abis/Makefile.am
new file mode 100644
index 0000000..8bdcc96
--- /dev/null
+++ b/include/osmocom/gsm/abis/Makefile.am
@@ -0,0 +1,3 @@
+osmoabis_HEADERS = e1_input.h subchan_demux.h ipaccess.h trau_frame.h
+
+osmoabisdir = $(includedir)/osmocom/gsm/abis