fwd_dct32x32 sse2: resolve missing declarations
fwd_dct32x32 sse2: resolve missing declarations

BUG=webm:1584

Change-Id: Ia2d9fcbccbad0c2142a3759e610670b86af0fef4

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