best way to use new qrupdate version?

[Jaroslav Hajek]

hi John,

in version 1.1, which I intend to release later this year, qrupdate
will be able to compute rank-1 updates of LU and pivoted LU
factorizations. The SVN version already has the functionality. I want
to make the feature again available to Octave via a "luupdate"
function. The bulk of the code for Octave is already upstream:
http://hg.savannah.gnu.org/hgweb/octave/rev/6f3ffe11d926

Because there is 100% backward compatibility, I would like Octave stay
buildable with qrupdate 1.0, which by now has already spread to
several distros. The approach I've taken in the above patch is simply
check for one of the new functions after qrupdate was detected, and
define an additional macro. But maybe that is not the best idea? Does
anyone see a better way?
qrupdate uses a F77-style implicit interface, so there is no header
file, which could define a versioning symbol.
An alternative is to make qrupdate 1.1 a requirement for Octave 3.4,
but it seems nice to support the old version if it's compatible.

comments?

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz