media-libs/opencv: revision bump to 3.1.0-r6

media-libs/opencv: revision bump to 3.1.0-r6

* Update SRC_URI to the new URLs
* Switch to downloading the tar.gz instead zip file
* Add git hash to end of contrib download to allow revision bumps
* Updated revision of contrib modules to fix various errors
* Remove Qt 4 support to follow the new Gentoo standard
* Use new OpenMP test logic
* Added patch to build against CUDA v8.
  Patch based on one submitted by Sven Eden
  Gentoo-bug: 598674
  Gentoo-bug: 597754
* Added Tesseract use flag and fixed building against it.
  Gentoo-bug: 572836
  Gentoo-bug: 584428
* Added use flag for the SFM module because of dependencies
  on several Google libraries
  Gentoo-bug: 597166
* Added use flag for the HDF module because of a dependency
  on media-libs/hdaf5
  Gentoo-bug: 596212
* Added use flag for the CVV module because it will silently
  fail if Qt 5 is not installed.
* Added patch to fix the finding of certain libraries
  Gentoo-Bug: 584478

Signed-off by: Jonathan Scruggs (j.scruggs@gmail.com)