Add sse4_1 functions for Intra-edge experiment:
  av1_filter_intra_edge_sse4_1()
  av1_filter_intra_edge_high_sse4_1()

Approx cycle reduction at qp 20, 1 kf:
  Enc (lbd) 1.4% to 0.3%
  Dec (lbd) 0.4% to 0.1%
  Enc (hbd) 1.1% to 0.2%
  Dec (hbd) 0.6% to 0.1%

No change to bitstream

Change-Id: I176b2d125424d7d226114c807915c33dde5c3720