modified OpenCL SURF API and the tests in 2.4.x to prove that it gives different from CPU results
made SURF_OCL default constructor parameters the same as SURF
modified SURF's performance test to test OpenCL version as well
fixed doc builder warnings; make sure the tests give reasonable results when OpenCL is not available
performance tests for ORB
made the example consistent with the fuction definition and improved doc

made the example consistent with the fuction definition and improved doc
1. fix an error in sample code
2. change an external link to maintain consistency with the previous tutorial
remove highlighting in some function links

1. Remove whole-document highlighting in some function links
2. fix the function alias `readwriteimagevideo`
Fixed Load, Modify, and Save an Image tutorial
Keep definitions of link aliases consistent
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making OCL tests conform to the comon style
disabling failing tests
Misprint fixed in table formatter
Fixed "Mat mask operations" tutorial. Thanks @RJ2 for pointing this.
Merge pull request #2520 from vlkolesnikov:misprint_fix
Removed obsolete list from docs
Merge pull request #2516 from Daniil-Osokin:fix_docs
Merge pull request #2521 from atrebbi:#3620
Merge pull request #2498 from dreamworld:fix_tutorial_mat_the_basic_image_container