Fixed flann build with NEON;
Fixed Haming distance with NEON;
Honest cvRound for WinRT added;
cvRound test added;
Video IO with direct show disabled;

After setting depth to CV_32F for non double types this produces difference in results. I've attached test that reproduce this issue.The issue was found during anali broken GPU tests  for multiply/device functions.

Overloaded PCA constructor and ( ) operator to implement Feature#2287 - PCA that retains a specified amount of variance from the data. A sample was added to samples/cpp to demonstrate the new functionality. Docs and Tests were also updated