refactor Makefile build rules, don't use the FORCE

The initial goal was to make sure we don't have overall FORCE rules causing
unnecessary rebuilds -- annoying while writing documentation. As I looked
through possible dependencies, I finally understood what's going on here.

Remove code dup and nicely sort which belongs where in build/Makefile.*.inc. In
each, describe in a top comment how to use it, and also unify how they are
used:

- Rename Makefile.inc to Makefile.docbook.inc and refactor
- Add Makefile.vty-reference.inc
- Add Makefile.common.inc

Make sure that we accurately pick up all dependencies.

Drop use of the macro called 'command', that silenced the actual command lines
invoked and replaced them with short strings: it obscures what is actually
going on and makes the Makefiles hard to read and understand.

Each manual's makefile is greatly reduced to few definitions and a Makefile
include, e.g. one for asciidoc, one for VTY reference.

Move common/bsc_vty_additions.xml to OsmoBSC/vty/libbsc_vty_additions.xml, link
from OsmoNITB. It applies only to OsmoBSC and OsmoNITB.

Add a script that combines a VTY reference file with *all* additions files
found in a manual's vty/ dir. Call this from Makefile.vty-reference.inc.

Change-Id: I9758e04162a480e28c7dc83475b514cf7fd25ec0

doc/manuals/Makefile

@@ -1,45 +1,11 @@
-# XSL stylesheets downloaded from http://docbook.sourceforge.net/release/xsl/current/html/
-# Makefile from BitBake/OpenEmbedded manuals
-
-EXTRA_DEPS = gen-vty-docbook
-
-topdir = .
-pcu_reference = $(topdir)/osmopcu-vty-reference.xml
-manuals = $(bts_manual) $(pcu_reference)
-# types = pdf txt rtf ps xhtml html man tex texi dvi
-# types = pdf txt
-types = $(docbooktotypes)
-docbooktotypes = pdf
-# htmlcssfile =
-# htmlcss =
-
-TOPDIR := ..
-ASCIIDOCS := osmopcu-usermanual osmopcu-gb
+TOPDIR = ..
 
+ASCIIDOC = osmopcu-usermanual.adoc osmopcu-gb.adoc
 include $(TOPDIR)/build/Makefile.asciidoc.inc
-include $(TOPDIR)/build/Makefile.inc
-
 osmopcu-gb.pdf: gb/*.adoc gb/*.msc
 osmopcu-usermanual.pdf: chapters/*.adoc
 
-clean:
-	-rm -rf $(cleanfiles)
-	-rm -rf gen-vty-docbook
-	-rm osmopcu-usermanual__*.png
-	-rm osmopcu-usermanual__*.svg
-	-rm osmopcu-usermanual.check
-
-gen-vty-docbook: FORCE
-	$(call command,xsltproc -o generated/combined1.xml \
-		--stringparam with $(PWD)/../common/vty_additions.xml \
-		$(MERGE_DOC) vty/osmo-pcu_vty_reference.xml, \
-		XSLTPROC,Merging Common VTY)
-	$(call command,xsltproc -o generated/combined2.xml \
-		--stringparam with $(PWD)/vty/osmo-pcu_vty_additions.xml \
-		$(MERGE_DOC) generated/combined1.xml, \
-		XSLTPROC,Merging PCU VTY)
-	$(call command,xsltproc ../vty_reference.xsl generated/combined2.xml > generated/docbook_vty.xml, \
-		XSLTPROC,Converting PCU VTY to DocBook)
-
-
+VTY_REFERENCE = osmopcu-vty-reference.xml
+include $(TOPDIR)/build/Makefile.vty-reference.inc
 
+include $(TOPDIR)/build/Makefile.common.inc