Added vp10_fht8x8_sse2() unit test

- Inherited base class TransformTestBase to derived class VP10Trans8x8HT.
- Employed RunCoeffCheck() to test vp10_fht8x8_sse2() against C reference
  function vp10_fht8x8_c().
- fdst8_sse2() related seven hybrid transform cases are covered in this
  test.
- Test passed (4 test cases w/o EXT_TX; 16 test cases with EXT_TX).

Change-Id: Id9a9b308c707164a120d9ceb2c30e572026fb1d0
2 files changed