Use same intra prediction for all block size

Use same intra prediction for all block size

The commmit changed to use same intra prediction function for all
block sizes.

Some details on the changes:
1. All directional modes except DC/TM/V/H now have built-in filtering
for all pixels with filter taps either (1, 2, 1)/4 or (1, 1)/2.
2. Above edge get automatic extended to double width (bw*2), which
makes a lot of the prediciton mode computation simpler.
3. Same intra prediction function is called with different size
for i4x4_pred and all other larger size.

Overall, the change helped keyframe only coding for both cif size
and std-hd size test sets by .5% consistently on all encodings.
For normal coding with single/auto key frame, the change now also
is consistently net positive for all encodings. The overall gains
is about .15% on std-hd set.

Change-Id: I01ceb31fbc73d49776262e6bdc06853b03bbd1d1