6622418: G1: assert(false,"Non-balanced monitor enter/exit!") fails
Summary: The mark-sweep compact (which we use for full gc) wrapper did not save the mark words for biased locked objects.  The fix is to trivially call the appropriate methods.
Reviewed-by: tonyp, ysr

Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr