Turns out, you can't use preprocessor directives inside macro arguments.
Who'd have thought?

Now it allows choosing between arbitrary implementation variants.

Reverts some changes in b8ed00bd

This reverts commit fba72cb6, reversing
changes made to 02131ffb.

Also cv::, cv::gpu:: and cv::ocl:: namespace prefixes can be safely omitted
inside CV_ENUM and CV_FLAGS

It is already marked as a gtest 1.7.0

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

Fixed issues: #2737 #2848

- add syntetic images generation function to ts
- use generated syntetic images