Add missing includes to simple_encode.h
Add missing includes to simple_encode.h

Change-Id: Ic3bb2450443c52ba3df1ed6729cecdab51245e76

ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx