out-of-tree documentation build

[Graham Percival]

Does anybody feel like working on the out-of-tree documentation build?
 That's the current release blocker, but you don't need GUB around to
build it.

mkdir ~/whatever/
cd ~/whatever
/path/to/git/configure --srcdir ~/path/to/git/
make
make doc

then debug.  Currently it's not finding version.itexi in
Documentation/out-www/ ... it gets built in Documentation/out/.
There's probably half a dozen such little problems.
If nobody wants to do it, I'll continue working on it in 23 hours.

Cheers,
- Graham