This fixes all problems from the article "Checking OpenCV with PVS-Studio"
<http://www.viva64.com/en/b/0191/> that are not already fixed and are
not in 3rdparty or the legacy module.

The problems fixed are two instances of useless code and one instance
of unspecified behavior (right-shifting a negative number).

Conflicts:

	modules/core/src/stat.cpp

In class Mat, "static MatExpr Mat::zeros(int ndims, const int* sz, int
type)" and "static MatExpr Mat::ones(int ndims, const int* sz, int
type)" are declared but never implemented. That means we can see their
manuals from
"http://docs.opencv.org/modules/core/doc/basic_structures.html" but we
can't use them. Here I tried to finish their implementation.
I have also changed MatOp_Initializer::assign to make it support
multi-dimension Mat.
Test cases are added in test_math.cpp as well.

decreased the number of tests in Core_Eigen, decreased the maximum matrix size in Core_SVD; now those tests take less time to complete

probably, ultimately fixed the problem of empty clusters in kmeans; added test for singular kmeans cases

added COVAR_ and SORT_ enums to core.hpp; fixed many, many VS2005, VS2010 and MinGW (GCC 4.5.2) warnings

reworked nearly all of the OpenCV tests (except for opencv_gpu tests) - they now use the Google Test engine.