Most of <machine/_types.h> was either unused, wrong, or identical across
all 32-/64-bit architectures.
I'm not a huge fan of <sys/_types.h> either, but moving the bits we need
up into there is a step forward.
Bug: 12213562
Change-Id: Id13551c78966e324beee2dd90c5575e37d2a71e6
9afe2884c7