The OD_FDST_16() and OD_IDST_16() macros were written for use in the
 OD_FDCT_32_ASYM macro which took asymmetrically scaled input and
 after running an asymmetric butterfly step, passed it through to
 the 16-point Type-II DCT and 16-point Type-IV DST.
Because the DST implementations were never tested as stand alone
 transforms, some of the signs from the butterfly step ended up inside
 the DST macros.
These extra operations will be addressed in a follow up patch.

Change-Id: I32f54a4bb70cd8fad4ae5646cfa4f5b14a0f969b