Turn on OpenCL by default
Refactor OpenCL search
Allow OpenCL acceleration in every OpenCV module
Move OpenCL SURF to nonfree module
SURF accuracy test is moved to nonfree
Trying to make ocl surf work

1. Added more sync to reduction.
2. Turned off Image2D feature. Probably its support is not detected correctly.
3. Temporary disabled descriptor tests - can't localize a problem of the ocl descriptor.
Refactor OpenCL initialization and allow to use ocl module witout explicit setup
Disable crashing ocl tests
Move OpenCl SURF perf tests to nonfree and fix build of samples
Fix build errors
Merge pull request #664 from taka-no-me/ocl

Move OpenCL SURF to nonfree module