- Code cleanup.

  - Fix multiplication overflow in scaled MV position.

  - Disable clipping of unscaled RPR motion vectors.

  - Disable sub-PU grouping optimization with RPR.

  - Interaction between RPR and BDOF.

  - Incorrect calculation of refHeight.

  - Incorrect clipping at picture border and insufficient picture buffer margin.

  - Unsafe use of reference picture PPS pointers.

Patch provided by Nan Hu
Reduces LD chroma loss of JVET-O0491

This reverts merge request !915

- In InterPrediction::rightShiftMSB, use existing floorLog2 function

- In addAvg_SSE, avoid unnecessary use of 32-bit path

- In copyBufferSimd, reduce number of loops

- In paddingSimd, take advantage of padding extent being either 1 or 2

- In addBIOAvg4_SSE, reduce number of operations and avoid nasty
Xmm register -> memory -> integer register path

Overall, a decoder runtime reduction of about 3% is expected