updated patch to bring in the first functions with "transparent API"
removed unnecessary opencl kernels
fixed few compile errors and doc build errors
fixed some more compile errors
another attempt to fix compile errors
added some diagnostic into Tonemap test
fixed failure in Tonemap test
fixed bug with cl_long size on Win32 (thanks to Aaron Kunze)
Merge pull request #1828 from SpecLad:merge-2.4
Merge pull request #1824 from vpisarev:ocl_experiments5
fixed kernel compilation
Merge pull request #1841 from ilya-lavrenov:ocl_kernel_compilation
fixed kernel compilation in imgproc module
eliminated warning C4267
Merge pull request #1848 from ilya-lavrenov:warn
Merge pull request #1847 from ilya-lavrenov:ocl_imgproc_fix
changed eps in Retina_OCL test
Merge pull request #1852 from ilya-lavrenov:ocl_retina
Gave cv::String appropriate += operators.

Note that since String is a reference to an immutable string,
this doesn't actually change the string; it just replaces *this
with a reference to the concatenated string.
Replaced most of the instances of "s = s +" with "s +=".

This resynchronizes master code with 2.4. I say "most", because I might
have missed some due to different spacing; I'll deal with those
instances later if I find them.