Replacing openjdk-6 with gcj-jdk as default java for mips{,el}

Hi,

(With my Java hat on and my Release hat off)

We are getting close to being able to remove openjdk-6 from sid and
testing.  However, there is major blocker, which is java-common itself
(and its default-* binaries).  mips and mipsel are the only two
architectures still using OpenJDK 6 as default java.

At the current time, OpenJDK 7 have not been successfully ported on
these architectures and it is my understanding that it is unlikely to
change in the near future.  This leaves gcj-jdk as the only viable
option for mips and mipsel.

I intend to implement these changes in java-common in about 14 days,
unless there are alternative solutions (that does not involve keeping
openjdk-6 around).

~Niels