- 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