Split out GPRS SM layer into its own file

Change-Id: Ie61d22e7868af6de73cdf9c731f07130b282599d
diff --git a/tests/sgsn/Makefile.am b/tests/sgsn/Makefile.am
index 9afe0f7..bdcd9b4 100644
--- a/tests/sgsn/Makefile.am
+++ b/tests/sgsn/Makefile.am
@@ -59,6 +59,7 @@
         $(top_builddir)/src/sgsn/gprs_llc_xid.o \
 	$(top_builddir)/src/sgsn/gprs_sndcp_xid.o \
         $(top_builddir)/src/sgsn/slhc.o \
+	$(top_builddir)/src/sgsn/gprs_sm.o \
         $(top_builddir)/src/sgsn/gprs_sndcp_comp.o \
         $(top_builddir)/src/sgsn/gprs_sndcp_pcomp.o \
         $(top_builddir)/src/sgsn/v42bis.o \