import oap_client into libosmogsm

This imports the code from osmo-msc 6afef893e17bce67e4d4119acd34d480ed03ba77
with minimal changes to make it compile.  Symbol renaming to osmo_
prefix is done separately in a follow-up patch to have a as-clean-as-possible
import first.

Change-Id: I9bc38102318da02d1fe46ef516df3cfd6bf8e3da
diff --git a/include/Makefile.am b/include/Makefile.am
index 38ba14c..ef8ec65 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -100,6 +100,7 @@
                        osmocom/gsm/prim.h \
                        osmocom/gsm/l1sap.h \
                        osmocom/gsm/oap.h \
+                       osmocom/gsm/oap_client.h \
                        osmocom/gsm/protocol/gsm_03_40.h \
                        osmocom/gsm/protocol/gsm_03_41.h \
                        osmocom/gsm/protocol/gsm_04_08.h \