Initial minimal OsmoHNBGW user manual

This adds a very basic OsmoHNBGW user manual with an "overview" and
"running" chapter.  It still misses any information on configuration.

Change-Id: I54825a4ce5a457f87b0618332347eed8ea54afcb
Closes: OS#2588
diff --git a/doc/manuals/Makefile.am b/doc/manuals/Makefile.am
index 91aa8f8..7a76e90 100644
--- a/doc/manuals/Makefile.am
+++ b/doc/manuals/Makefile.am
@@ -1,9 +1,16 @@
 EXTRA_DIST = \
+	     osmohnbgw-usermanual.adoc \
+	     osmohnbgw-usermanual-docinfo.xml \
+	     chapters \
 	     osmohnbgw-vty-reference.xml \
 	     regen_doc.sh \
 	     vty
 
 if BUILD_MANUALS
+  ASCIIDOC = osmohnbgw-usermanual.adoc
+  ASCIIDOC_DEPS = $(srcdir)/chapters/*.adoc
+  include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.asciidoc.inc
+
   VTY_REFERENCE = osmohnbgw-vty-reference.xml
   include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.vty-reference.inc