RFR (14) 8237348: Javadoc of MemorySegment::allocateNative should state that memory is zero-initialized

[Maurizio Cimadamore]

Hi,
there is a mistake in the javadoc of MemorySegment::allocateNative -as 
the javadoc says that the initialization state is unspecified, where in 
reality we do call setMemory on the allocated block (so that memory 
contents are set to zero).

Webrev:

http://cr.openjdk.java.net/~mcimadamore/8237348/

Cheers
Maurizio