- Use range check function to avoid DCT_DCT overflow.
  We need to re-develop the column txfm side scaling/rounding. Now,
  we prefer to maintain the current BDRate level.
- Encoder user level time reduction <1% owing to av1_fht32x32_avx2.
- Add MemCheck unit test and fdct32() unit test.

Change-Id: I1e67030f67bc637859798ebe2f6698afffb8531c