See 092f916d for explanation.

This reverts commit 4f9c081d.

OpenCV Error: Unknown error code -6 (OpenCL function is not available: [clGetPlatformIDs]) in opencl_check_fn, file /home/ahb/software/opencv/modules/ocl/src/cl_runtime/cl_runtime.cpp, line 83

The issue results from modules/ocl/src/cl_runtime/cl_runtime.cpp checking for
"linux" instead of "__linux__" (cp.  http://sourceforge.net/p/predef/wiki/OperatingSystems/)

Adjust all other occurrences of "defined(linux)" as well.

See also #2101

Fixed a valgrind 'Conditional jump or move depends on uninitialised value(s)' on cv::kmeans(...). The original code used points(sampleCount, 1, CV_32FC2), which confused generateCentersPP into thinking it is a 1 dimensional center, instead of 2. As a result it would set only the x variable and leave y unitialised.

Fix compilation erros when compiling this constructor.
First argument type of "convertTo" should be instance, not a pointer of instance.

First pull request was created for master branch.
But it should be marged for 2.4.
https://github.com/Itseez/opencv/pull/2113

Fix: freeing previous elements has to be done before loading new parameters to avoid trying to delete unexisting objects if arrays size was modified

Also deleted miscellaneous remaining multimon cruft.
Deleted #include <winuser.h>, because <windows.h> includes it
already.

This should have a nice side effect of preventing us from
accidentally using any Windows API that's too new.