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/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 900fcfa..29299a6 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -30,7 +30,7 @@
 			milenage/aes-internal.c milenage/aes-internal-enc.c \
 			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
 			gsup.c gprs_gea.c gsm0503_conv.c oap.c gsm0808_utils.c \
-			gsm23003.c mncc.c bts_features.c
+			gsm23003.c mncc.c bts_features.c oap_client.c
 libgsmint_la_LDFLAGS = -no-undefined
 libgsmint_la_LIBADD = $(top_builddir)/src/libosmocore.la