8176195: Fix misc module dependencies in jdk_core tests
Reviewed-by: mchung

4774077: Use covariant return types in the NIO buffer hierarchy
Reviewed-by: psandoz, alanb, mr, darcy

6943119: Rebrand source copyright notices
Reviewed-by: darcy, weijun

6920732: opensource test/java/nio/charset
Summary: move the test cases to openjdk
Reviewed-by: martin