tests: Introduce a very basic gsm0808 test

This tests verifies the content of the GSM 08.08 messages, it does
not verify the remaining headroom (which the SCCP/IPA code relies
on being plenty to prepend the header). More to come in the future.
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 6aae04d..69624c1 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -65,3 +65,9 @@
 cat $abs_srcdir/lapd/lapd_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/lapd/lapd_test], [], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([gsm0808])
+AT_KEYWORDS([gsm0808])
+cat $abs_srcdir/gsm0808/gsm0808_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/gsm0808/gsm0808_test], [], [expout], [ignore])
+AT_CLEANUP