Env setup for testing package implemented using /etc/profile.d;
Variable with path for all native samples added;
Path for test binaries and test data updated.

fill destination matrix with zeros if it was reallocated

Fixed bug #3489: The code assumed that two global variables would be constructed in a particular order, but global variable initialization order is compiler-dependent.

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.