asciidoc 7.0.4 and newer considers such includes from parent directory
unsafe.
Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Documentation/Makefile spent a lot of time to generate include
dependencies, which was quite noticeable especially during "make clean".
Rewrite it to generate just a single dependency file.
Signed-off-by: Junio C Hamano <junkio@cox.net>