updated OpenGL functionality:

* 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
Tutorial for ARM Linux cross compilation added.
add openCLExecuteKernelInterop method
Switched to TEST_CYCLE_MULTIRUN for fast tests
Increased time limits
optimized DeviceInfo class and ensureSizeIsEnough
Merge pull request #508 from bitwangyaoyao:2.4_interpKernel
Test system refactoring

cmpEps replaced on cmpEps2 to reduce code dublication;
Constants for cmpEps return values added.
Add auto detection to Intel OCL
cv::Ptr description extended.
restored binary compatibility
Merge pull request #512 from jet47:core-gpu-updates
Merge pull request #440 from AnnaKogan8:fixed-perfomance-tests
restored source compatibility
Merge pull request #519 from bitwangyaoyao:2.4_findOCL
Merge pull request #498 from asmorkalov:doc_ptr
OpenCV 2.4.4 preparation

Manager verison incremented;
Additional constatnt for library intialization added;
Documents updated.
Merge pull request #502 from jet47:opengl-updates
updated gpu module API
Fixed documentation build