Update segmentation.cpp

Added detailed comments to watershed()
Add method in StatModel class, to load from String

Added a method "loadFromString" which is based on the "load" one. It
allow to directly pass the XML string which can be usefull and faster
when you have a huge file in a variable.
Changing tabs to spaces.

Edited previous code to change tabs into spaces.
Re-editing Documentation

Attempting to re-editing the documentation, to satisfy buildbot error
status.
Re-edition of documentation

Re-edited the documentation again.
Build separate world-like iOS framework for contrib
highgui: Support to change trackbar count in setTrackbarPos and replaced deprecated CreateToolbarEx in Windows.
Fix SymmColumnSmallVec_32s16s SSE code
Specifically, in general antisymmetric case src[-1] (S0) should be
subtracted from from src[1] (S2), and not the opposite.
Removed "FORMAT_XML" to generalize format

Removed the "FileStorage::FORMAT_XML" to generalize format of the String
model.
Update segmentation.cpp

removed trailing whitespaces
Added better OpenNI2 support to the Asus Xtion and Occipital Structure
sensors which do not have image generators.
update android.toolchain.cmake
Merge pull request #3448 from Ashod:highgui_trackbar_improvements
Merge pull request #3473 from TobyWanKenobi:master
Merge pull request #3491 from mshabunin:ios-extra-world
Remove unnecessary local variable "size".

It should also be better for optimizing when compiling kernel.

Signed-off-by: Yan Wang <yan.wang@linux.intel.com>
Merge pull request #3517 from wangyan42164:ocl_denoising_2
Merge pull request #3528 from ilya-lavrenov:update_android_cmake
fix obvious copy+paste typo in computeDistance()

(with this else-branch, argument contour2 would not be used at all)
Merge pull request #3519 from fvgoto:patch-1