Log Message:
opencv: version 3.4.17 with proper explicit BLAS (CBLAS + LAPACKE) usage

This does the small bugfix update from 3.4.16 to 3.4.17 and adds proper usage
of BLAS stuff. There was linkage to BLAS before via numpy, but the internal
explicit BLAS-using code was not built, as the CMake machinery did not find it.

This commit drops an actually counterproductive patch and adds pkg-config
calls to find the BLAS-related libraries. Note that vor opencv-contrib-face,
the BLAS choice during its build doesn't really enter the result, apparently,
but the build process does use it and it would not help to confuse matters there.

I am not sure if the buildlink3.mk should also add blas.buildlink3.mk now. It
does not feature numpy right now. Should it?

Next step should be move towards 4.x at least.

Upstream:

December, 2021

OpenCV 3.4.17 has been released. Bug fixes, optimizations and other enhancements
are propagated into OpenCV 4.5.5.

Long-lived OpenCV 3.x release series is here since 2015. We are going to reduce
support of 3.x branch in the future to move forward to OpenCV 5.0.