Track libcore.os' move to android.system.

(This is partial, but should cover everything in AOSP master except
for the zygote.)

Change-Id: I1042c99245765746a744c44e714095cb2c6cb75d
Merge "Track libcore.os' move to android.system."
Fix build.

Change-Id: I0bd6e1aac19276bf664accd8d38f86d2cc7450cc
Merge "Fix build."
Merge remote-tracking branch 'aosp/master' into fml-master