Classloader changes

[Conor MacNeill <co...@cortexebusiness.com.au>]

I have changed most usages of the AntClassLoader to defer to the parent
classloader first. This makes the classloader "well behaved". I think this
is appropriate in most instances such as <taskdef>, <property>,
<available>. It is, however, a potential backward compatability issue. I
want to see how the next Gump run goes to see the impact.

In general, problems arising from this change will mostly affect classes
which dynamically load other classes. For this reason, the <java> task and
<junit> task's retain their current usage. I plan to add some code to set
the context class loader for later VMs. This will require tedious
reflection based code. I am also studying ways to improve the junit and
java tasks.

Conor