by using the indices from the sorted distance vector of pairs.

In case of binary class, pred_m is initialized as zero vector and later
returned when raw outputs are requested, but it is never filled.

Fixed getSubset method to support Nx3 1-channel matrices as input (3xN 1-channel matrices doesn't supported at all).

Added test for checking that solvePnPRansac accepts vector<Point3f> and Nx3 1-channel or 1xN/Nx1 3-channel matrices as input.

Changed parameter order in documentation of findEssentialMat, because threshold and probability were switched.

related to issue 4969
fixes issue 5891
fixes issue 5922

and fix the compilation for iOS in the same time

The Android NDK would be moving to Clang as its default compiler
in the future. This patch allows OpenCV to build with the default
c++_shared / c++_static

TEST=Builds OpenCV with -DANDROID_TOOLCHAIN_NAME=
aarch64-linux-android-clang3.6 -DANDROID_STL=c++_shared