Original error without the fix:

opencv/modules/objdetect/src/cascadedetect.cpp: In member function 'bool cv::CascadeClassifierImpl::ocl_detectSingleScale(const cv::_InputArray&, cv::Size, int, double, cv::Size)':
/opencv/modules/objdetect/src/cascadedetect.cpp:1215:
error: no matching function for call to 'cv::ocl::Kernel::args(cv::ocl::KernelArg, cv::ocl::KernelArg, cv::ocl::KernelArg, int, cv::ocl::KernelArg, cv::ocl::KernelArg, cv::ocl::KernelArg, cv::Size&, int&, float, cv::Rect&, cv::Size&, cv::CascadeClassifierImpl::<anonymous enum>)'

Fix a bug in the er tree clean-up process (see discussion in https://github.com/Itseez/opencv/pull/1520). It's not necessary to walk the er tree in order to clean up the memory since it's possible to cleanup the regions in the stack just by iterating over the er_stack vector instead of walking the tree structure. This turns out to be safer because the tree structure of those regions may have been modified previously in er_save function.

Updated documentation and sample to use the new function API

Added erGrouping function: Find groups of Extremal Regions that are organized as text blocks. Updated sample/cpp to use the complete text detection pipeline

first parameter of createERFilterNM1/createERFilterNM2 is now mandatory. changed the sample program to use the new prototypes

renamed getDefaultClassifierNM{1,2}() to loadClassifierNM{1,2}() and added "const std::string& filename" parameter (mandatory).

functions getDefaultClassifierNM1() and getDefaultClassifierNM2() allow to implicitly load the default classifiers when creating a ERFilter object