6578152: fill_region_with_object has usability and safety issues Reviewed-by: apetrusenko, ysr

6782457: CMS: Livelock in CompactibleFreeListSpace::block_size() 6736295: SIGSEGV in product jvm, assertion "these are the only valid states during a mark sweep" in fastdebug Summary: Restructured the code in the perm gen allocation retry loop so as to avoid "safepoint-blocking" on locks, in this case the Heap_lock, while holding uninitialized allocated heap storage. Reviewed-by: apetrusenko, iveresov, jcoomes, jmasa, poonam