small incremental improvement

[Jonathan Locke <jo...@eidolon.muppetlabs.com>]

hi i'm new to this list, so i don't yet know how things are done... but
please find attached a new Main.java which provides a -interactive flag
which keeps ant from exiting its VM.  on my machine with my work habits,
this results in compiles that are several times faster when doing many
rebuilds (with the same options) in a row because the vm doesn't have to
spend all that time shutting down just to start up again... plus hotspot
has more of a chance to do its magic which is very cool!

i'm not sure that my modifications are exactly what others would want in
the way of this feature, but i tried to adapt to the coding style and i
tried not to break anything (no guarantees, it's just a quick hack!). a
code review would be a good idea if anyone likes the idea enough to
consider checking it in.

thanks for a great tool!

take care,

    jon