[foreign-memaccess] RFR 8227285: Fix memory access API naming issues

[Maurizio Cimadamore]

Hi,
this patch fixes the naming and doc issues mentioned here:

https://mail.openjdk.java.net/pipermail/panama-dev/2019-July/005907.html

Webrev:

http://cr.openjdk.java.net/~mcimadamore/panama/8227285/

Javadoc:

cr.openjdk.java.net/~mcimadamore/panama/8227285_javadoc

note: this patch is based on top of the changes in 8227278

Cheers
Maurizio