Hi,

parallel-mode should be back to usable. Note, I didn't try to clean-up 
the tangle of includes we have in parallel-mode files, a lot can be 
improved, for sure. I also added gates for the *_debug.cc pb_ds 
testfiles, otherwise all spuriously fail in check-parallel, etc.

Tested x86_64-linux normal, debug, parallel modes. Committed to mainline.

Paolo.

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