[nicl] RFR 8198960: Move MemoryRegion in implementation package

[Maurizio Cimadamore]

Hi,
the MemoryRegion interface is only used within the implementation 
packages and should therefore be removed from the public API.

http://cr.openjdk.java.net/~mcimadamore/panama/8198960/

P.S.
I've tweaked the test "Hello.java" as it was failing in my Linux setup 
because of case-sensitivity.

Cheers
Maurizio