Zero buildable again with IcedTea7 HEAD

[Andrew Hughes]

For details, see the blog:

http://blog.fuseyism.com/index.php/2012/07/26/the-return-of-zero-sort-of/

With this change, if --enable-zero is passed to configure, it will use our
existing hotspot.map support to switch to the HotSpot tree from the 2.1
branch (i.e. the last buildable version, where the ARM work is going on).

I hope this should enable us to support Zero without having to maintain
the whole of 2.1 (i.e. CORBA, JDK, etc.) indefinitely.

Thanks,
-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

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