cvStereoRectify assumes that NULL is provided in case of no distCoeffs

The inner loop of the backward scan got the wrong initial "a".

OpenCV 3.0.0

* tag '3.0.0':
  Version for 3.0.0 release

Small typo fix in the documentation.
It was written 'devie' instead of 'device' in: 'Switching active device can be done using cuda::setDevice() function'

made improvements in ECC code (comments from https://github.com/Itseez/opencv/pull/3845), as well as minor tweak in pthread's based parallel for.

removing trailing whitespaces

Compilation error on Mac fix & warning on android

Warnings fixed on iOs