Implement ITU-T I.460 multiplex / demultiplex

This implements a multiplexer and de-multiplexer for the ITU-T I.460
standard.  The latter covers the transmission of sub-slots of 32/16/8k
inside 64k timeslots.

Change-Id: Id522f06e73b77332b437b7a27e4966872da70eda
diff --git a/tests/testsuite.at b/tests/testsuite.at
index bab5730..4ff6671 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -375,3 +375,9 @@
 cat $abs_srcdir/exec/exec_test.err > experr
 AT_CHECK([$abs_top_builddir/tests/exec/exec_test], [0], [expout], [experr])
 AT_CLEANUP
+
+AT_SETUP([i460_mux])
+AT_KEYWORDS([i460_mux])
+cat $abs_srcdir/i460_mux/i460_mux_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/i460_mux/i460_mux_test], [0], [expout], [ignore])
+AT_CLEANUP