6951188: CMS: move PromotionInfo into its own file
Summary: Moved PromotionInfo and friends into new files promotionInfo.{h,c}pp from their previous compactibleFreeListSpace.{h,c}pp home.
Reviewed-by: apetrusenko
6919638: CMS: ExplicitGCInvokesConcurrent misinteracts with gc locker
Summary: GC-locker induced concurrent full gc should be asynchronous; policy now controlled by a separate flag, which defaults to false.
Reviewed-by: jmasa