import gprs_gsup_message.[ch] from openbsc as gsup.[ch]

Move those routines from OpenBSC to libosmogsm, so they can be
re-used from other programs.  I think it was a mistake to add them only
inside the openbsc repository in the first place.  We need to pay more
attention to this in the future.
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 762b10a..aa269af 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -190,3 +190,9 @@
 cat $abs_srcdir/tlv/tlv_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/tlv/tlv_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([gsup])
+AT_KEYWORDS([gsup])
+cat $abs_srcdir/gsup/gsup_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/gsup/gsup_test], [0], [expout], [ignore])
+AT_CLEANUP