contrib/subtree/Makefile: clean up rules to generate documentation
git:Documentation/Makefile establishes asciidoc/xmlto calls as being
handled through their appropriate variables, Hence, change to bring into
congruency with.
Similarly, MANPAGE_XSL exists in git:Documentation/Makefile, while
MANPAGE_NORMAL_XSL does not outside contrib/subtree. Hence, replace
MANPAGE_NORMAL_XSL with MANPAGE_XSL.
Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: James Denholm <nod.helm@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>