Annnotate libcore.io.Memory as @SystemApi

Bug: 157639992
Test: m droid
Merged-In: I201510d3c5205305228ac6358f19ae13d31cf421
Change-Id: I201510d3c5205305228ac6358f19ae13d31cf421
(cherry picked from commit d81f169c392df99869a5c5ab025608ec5e358768)
6 files changed