freeze exception for cacao-oj6

[Matthias Klose <doko@cs.tu-berlin.de>]

proposing a freeze exception for cacao-oj6 for testing. cacao-oj6 is a
copy of the openjdk-6 package with the cacao sources
included. Compared to openjdk-6 on architectures without the Hotspot
JIT support, cacao-oj6 (including a JIT) is a much faster JVM on the
architectures where it does build (powerpc, s390, armel for
now). Discussed this at Debconf with some people. I was told to get
agreement with debian-security about the maintainability (because of
the duplicate sources). See #495256 as well.

  Matthias