gauss_w_lut is a statically defined variable of type oclMat.  The oclMat
destructor calls openCLFree() which via getInitializationMutex() accesses
the __module variable which has been statically defined in cl_context.cpp

Since the destruction order of statically defined variables in different
compilation units is undefined, it is possible that __module will
be destructed before gauss_w_lut, which would result in a segfault when
getInitializationMutex() is called while destructing gauss_w_lut.

In order to avoid this issue, we need to make gauss_w_lut a private
member of the HOGDescriptors class so we know it will be destroyed
before __module.

Affected functions surf.ocl, pyrlk.ocl and hog.ocl are updated with the change.

change the download channels to oclchannles()
fix bugs of arithm functions
perf fix of bilateral
bug fix of split test case
add build_warps functions