Fix warnings about missing parent for class members
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
Fix several inconsistent declarations identified by check_doc2 script
Add support for enums into rst ocv domain
Whitelist functions/structs in check_docs2 that are impossible to fix in 2.4
Merge pull request #492 from taka-no-me:fix_warnings_gcov
Merge pull request #500 from nielsgm:predict_python_wrapper_to_docs
Merge pull request #503 from taka-no-me:fix_docs
Update samples/python2/hist.py

range in calcHist() changed from [0,255] to [0,256]. Otherwise, it won't count pixels with value 255. It can be verified taking sum of histogram values and checking it with image size.
Merge pull request #505 from abidrahmank:2.4
Merge branch '2.4'
Tutorial for ARM Linux cross compilation added.
add openCLExecuteKernelInterop method
Fix documentation problems found by check_docs2 script
Fix warnings from documentation build
Merge pull request #509 from taka-no-me:fix_docs_master
Switched to TEST_CYCLE_MULTIRUN for fast tests
Increased time limits
Added Thin Prism Distortion Model

Only the code.
Thin prism distortion model added doc

Thin prism distortion model added to the
camera_calibration_and_3d_reconstruction.rst