The user/specs docs now have external references support.
Developers doc are not installed so they do not participate.
However, using a similar makefile shared amongst developers
document reduces maintenance and is forward looking.
Man pages being out of here, reorg developers docs under the same roof.
Drop the obsolete sgml subdir.
Reviewed-by Jeremy Huddleston <jeremyhu@apple.com>
Signed-off-by: Gaetan Nadon <memsize@videotron.ca>
Signed-off-by: Keith Packard <keithp@keithp.com>
