Fixed errors in parallel_for based on pthreads

Fixing compiler errore & removing whitespaces

Fixing prallel_for_pthreads error and warnings on win

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