(cherry picked from commit 887736bc)

(cherry picked from commit 1b8c2589)

Correction of the integer data treated as floating point data bug, already corrected in the 2.4 branch.

initial commit; ml has been refactored; it compiles and the tests run well; some other modules, apps and samples do not compile; to be fixed

This should allow many algorithms to take advantage of more parallelization
technologies.

Made all STL usages explicit to be able automatically find all usages of
particular class or function.

fixed warnings in gbt; added insertChannel() and extractChannel(); made the code "rand{u|n}(arr, <number>, <number>)" work properly.

minor fixes in CvGBTrees, its test and sample

opencv/modules/ml/src/gbt.cpp
 

Gradient Boosting Trees (CvGBTrees) added to opencv mll. Test for all CvGBTrees public methods added.