Fix#3714:Improve Display Image Tutorial

For Bug #3714, user use the imshow() function without calling
namedWindow() properly, because user did not know the implicit rule for
imshow(). (i.e. without calling namedWindow implied calling namedWindow(
,CV__WINDOW_AUTOSIZE).

Improve the Display Image Tutorial to educate the user for such implied
rule.

Put a note on documentation for Bug#3714

Revise the documentation regarding to imshow() function to better
educate the user the implicit rule. (i.e. without creating the window
before the imshow() function is the same as creating AUTOSIZE window)
minor fix to make "updateBackgroundModel=false" option meaningful.
highgui: Support to change trackbar count in setTrackbarPos and replaced deprecated CreateToolbarEx in Windows.
ability to enable OpenMP simultaneously with other parallel framework
Fixed typos in latentSVM detector demo.
export thread control to generated wrappers
add extra to FeatureDetector docs
fix bug 2432 for 2.4 branch
Merge pull request #3449 from Ashod:2.4_highgui_trackbar_improvements
Merge pull request #3498 from ilya-lavrenov:omp
Some changes to make migration to 3.0 easier
update android.toolchain.cmake
Merge pull request #3522 from ilya-lavrenov:update_android_toolchain_cmake
Fix memory leaks appearing when cvOpenFileStorage throws
Merge pull request #3515 from StevenPuttemans:fix_FeatureDetector_docs
Merge pull request #3500 from StevenPuttemans:fix_2432_2.4
Merge pull request #3514 from mshabunin:compat-24
Merge pull request #3511 from mattip:2.4
Merge pull request #3484 from euphrat:gmg_update_fix
Merge pull request #3471 from HelenWong:FixBug3714