Bug#547969: ivy jar not added to ant lib

[Patrick McFarland]

I would also like to see Ivy added to ant/lib. Ivy is a special case
in that it is a sister
project to Ant and people expect Ivy to work by default when installing it.

I find a dpkg configure option an acceptable alternative to blindly
symlinking ivy.jar to
the ant/lib director, as in, ask the user if he wants to do it
(defaulting to yes).