DisparityWLSFilter demonstrated the best results, so I removed all the other
filters. Quality was significantly improved by adding confidence support
to the filter (left-right consistency + penalty for areas near depth discontinuities).
Filter was optimized using parallel_for_ and HAL intrinsics. Demo application was
rewritten for better compliance with OpenCV standards. Added accuracy and
performance tests. Documentation was added, as well as references to the
original papers.

avoid overflow in histogram access

vs2010 does not know, ceil, floor, round and friends.

also, those are plain integer divisions, that do not need floor at all.

Added basic interface and demo for disparity filtering, added unoptimized fast weighted least
squares filter implementation. Current demo tests domain transform, guided and
weighted least squares filters on a dataset, measures speed and quality.

Adaptive manifold filter changes: Memory consuming was reduced and performance was improved (10% average).

the exact warnings are:
/builds/precommit-contrib_macosx/opencv_contrib/modules/ximgproc/samples/seeds.cpp:32:6: warning: no previous prototype for function 'trackbarChanged' [-Wmissing-prototypes]
/builds/precommit-contrib_macosx/opencv_contrib/modules/ximgproc/samples/seeds.cpp:32:26: warning: unused parameter 'pos' [-Wunused-parameter]
/builds/precommit-contrib_macosx/opencv_contrib/modules/ximgproc/samples/seeds.cpp:32:37: warning: unused parameter 'data' [-Wunused-parameter]

RFFeatureGetter* ->  Ptr<RFFeatureGetter> (need this for python wrapper and proper pointer handling)

Removed macros for generation Python wrapper to overcome build error, caused nested ximgproc namespace.