WIP: docs build in meson
I've found the start of a solution for the docs build in meson that doesn't involve recreating all the xorg-macros docbook build stuff: Use the same hotdoc pipeline that gnome and gstreamer are using.
- Fix up previous macro-substitution stuff (
- Figure out if we can avoid the gross hack at the end.
- Compare the html before/after on the xfree86 and dmx docs to make sure we haven't regressed.
Part of !31