Add VTY reference manual

Fixes: OS#2589
Change-Id: I042734fa9979b598d5471839e408cbf39bba57b5
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 81a25e2..eeed875 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -1,4 +1,7 @@
-SUBDIRS = examples
+SUBDIRS = \
+	  examples \
+	  manuals \
+	  $(NULL)
 
 EXTRA_DIST = \
   hnb_cs_lu.msc \