Summary: Minor code changes to cleanup warnings in java.util.*
Reviewed-by: mduigou, naoto, smarks
Contributed-by: NRemi Forax <forax@univ-mlv.fr>

Summary: to use new InternalError constructor with cause chainning
Reviewed-by: alanb, ksrini, xuelei, neugens
Contributed-by: sebastian.sickelmann@gmx.de

Reviewed-by: dholmes

5045147: Prevent insertion of null Key into empty TreeMap (and null element into TreeSet) when no Comparator is used. Prevent insertion of key of incorrect type into empty TreeMap and incorrect type element into TreeSet and incorrect type when Comparator is used.
Reviewed-by: alanb, dl, mduigou

Reviewed-by: xdono

Reviewed-by: darcy, lancea, alanb, briangoetz, mduigou, mchung

Reviewed-by: chegar, dholmes

Reviewed-by: alanb, briangoetz

Reviewed-by: darcy, weijun

6800572: Removing elements from views of NavigableMap implementations does not always work correctly.
Summary: Replace use of new TreeSet with new KeySet
Reviewed-by: martin

6691185: (coll) TreeMap.navigableKeySet's descendingIterator method starts at first instead of last entry
Reviewed-by: dl, chegar