* removed OpenGLFuncTab, now extensions are loaded internally
* added support of GlBuffer and GlTexture2D to InputArray/OutputArray
* added ELEMENT_ARRAY_BUFFER and PIXEL_PACK_BUFFER targets
* added copyFrom/copyTo method for GlBuffer and GlTexture2D
* removed GlFont
* removed pointCloudShow
* removed OpenGLCleanCallback
* added Access parameter to GlBuffer::mapHost
* added autoRelease parameter to all create methods

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

make Mat::Mat(CvMat* m) return empty matrix when m is NULL; added utility Mat::initEmpty() method to replace duplicated matrix initializations in different constructors

fixed a few compile problems in SparseMat code; fixed iteration over an empty sparse matrix (ticket #1587)

Input/Output arrays are updated to support fixed-type and fixed-size semantic for all compatible types