Without proposed change, module throws build error regarding missing `opencv2/cudaimgproc.hpp`

This suppresses the interpretation of string literals by switching the ocv_download_log from a macro to a function.
This avoid crashes when the string to log contains escape characters.

More details about the problem this PR fixes are available at: https://github.com/opencv/opencv_contrib/issues/1131

* optimized cv::decolor by removing vector.push_back

* restored CV_INSTRUMENT_REGION() and original indent

* fix build warnings in contrast_preserve.hpp

* undo refactoring contrast_preserve.cpp/hpp

  * avoid misuse of vzeroupper on Visual Studio 2013 Update 5
  * add ifdef to avoid unattended optimization

- bgfg_segm
- peopledetect
- opencv_version
- dnn/colorization
- tapi/opencl_custom_kernel
- tapi/dense_optical_flow (renamed tvl1_optical_flow)

  * avoid aggressive optimization on Visual Studio 2012 Update 5
  * add code branch to avoid unattended optimization (keep the old code)

* SSE2 : use _mm_cvtpd_epi32 when converting from CV_64F to CV_32S

* No need to define a new universal intrinsic

* clean npr functions of useless initializations (speed-up)

* photo: remove unnecessary code