Makefile: build all manuals in $(O)/docs/manual

Like Arnouts' patch originally did.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

Makefile

@@ -716,19 +716,13 @@ release:
 define GENDOC_INNER
 $(1): $(1)-$(3)
 .PHONY: $(1)-$(3)
-$(1)-$(3): $$(O)/docs/$(1)/$(2)/$(1).$(4)
+$(1)-$(3): $$(O)/docs/$(1)/$(1).$(4)
 
-$$(O)/docs/$(1)/$(2)/$(1).$(4): docs/$(1)/$(1).txt $$($(call UPPERCASE,$(1))_SOURCES)
+$$(O)/docs/$(1)/$(1).$(4): docs/$(1)/$(1).txt $$($(call UPPERCASE,$(1))_SOURCES)
 	@echo "Generating $(5) $(1)..."
 	$(Q)mkdir -p $$(O)/docs/$(1)/$(2)
 	$(Q)a2x $(6) -f $(2) -d book -L -r $(TOPDIR)/docs/images \
 	  -D $$(@D) $$<
-
-clean-$(1): clean-$(1)-$(3)
-.PHONY: clean-$(1)-$(3)
-clean-$(1)-$(3):
-	$(Q)$(RM) -rf $(O)/docs/$(1)/$(2)
-
 endef
 
 ################################################################################
@@ -746,6 +740,8 @@ $(call GENDOC_INNER,$(1),pdf,pdf,pdf,PDF,--dblatex-opts "-P latex.output.revhist
 $(call GENDOC_INNER,$(1),text,txt,text,Text)
 $(call GENDOC_INNER,$(1),epub,epub,epub,EPUB)
 clean: clean-$(1)
+clean-$(1):
+	$(Q)$(RM) -rf $(O)/docs/$(1)
 .PHONY: $(1) clean-$(1)
 endef