Re-introduce openjdk6 build
Re-introduce openjdk6 build

Fixes #1577.

ashleyfrieze/junit,panchenko/junit,panchenko/junit,junit-team/junit4,junit-team/junit,junit-team/junit,junit-team/junit4,stefanbirkner/junit,kcooney/junit,ashleyfrieze/junit,junit-team/junit4,kcooney/junit,panchenko/junit,junit-team/junit,stefanbirkner/junit,kcooney/junit,ashleyfrieze/junit,stefanbirkner/junit