Summary: All of the hashing based Map implementations: HashMap, Hashtable, LinkedHashMap, WeakHashMap and ConcurrentHashMap are modified to use an enhanced hashing algorithm for string keys when the capacity of the hash table has ever grown beyond 512 entries. The enhanced hashing implementation uses the murmur3 hashing algorithm along with random hash seeds and index masks. These enhancements mitigate cases where colliding String hash values could result in a performance bottleneck.
Reviewed-by: alanb, forax, dl

7044486: open jdk repos have files with incorrect copyright headers, which can end up in src bundles
Reviewed-by: ohair, trims

Summary: Do not synchronize on self while writing hash table elements
Reviewed-by: alanb, mduigou
Contributed-by: NNeil Richards <neil.richards@ngmr.net>

Summary: No longer synchronize on self while writing other objects.
Reviewed-by: alanb, forax, mduigou, peterjones
Contributed-by: NNeil Richards <neil.richards@ngmr.net>