Merge pull request opencv#15980 from SSteve:doxygen_links

doc/tutorials/introduction/cross_referencing/tutorial_cross_referencing.markdown

@@ -4,7 +4,7 @@ Cross referencing OpenCV from other Doxygen projects {#tutorial_cross_referencin
 Cross referencing OpenCV
 ------------------------
 
-[Doxygen](https://www.stack.nl/~dimitri/doxygen/) is a tool to generate
+[Doxygen](http://www.doxygen.nl) is a tool to generate
 documentations like the OpenCV documentation you are reading right now.
 It is used by a variety of software projects and if you happen to use it
 to generate your own documentation, and you are using OpenCV inside your
@@ -57,5 +57,5 @@ contain a `your_project.tag` file in its root directory.
 References
 ----------
 
-- [Doxygen: Linking to external documentation](https://www.stack.nl/~dimitri/doxygen/manual/external.html)
+- [Doxygen: Linking to external documentation](http://www.doxygen.nl/manual/external.html)
 - [opencv.tag](opencv.tag)

doc/tutorials/introduction/documenting_opencv/documentation_tutorial.markdown

@@ -684,12 +684,12 @@ References {#tutorial_documentation_refs}
 - [Command reference] - supported commands and their parameters
 
 <!-- invisible references list -->
-[Doxygen]: http://www.stack.nl/~dimitri/doxygen/index.html)
-[Doxygen download]: http://www.stack.nl/~dimitri/doxygen/download.html
-[Doxygen installation]: http://www.stack.nl/~dimitri/doxygen/manual/install.html
-[Documenting basics]: http://www.stack.nl/~dimitri/doxygen/manual/docblocks.html
-[Markdown support]: http://www.stack.nl/~dimitri/doxygen/manual/markdown.html
-[Formulas support]: http://www.stack.nl/~dimitri/doxygen/manual/formulas.html
+[Doxygen]: http://www.doxygen.nl
+[Doxygen download]: http://doxygen.nl/download.html
+[Doxygen installation]: http://doxygen.nl/manual/install.html
+[Documenting basics]: http://www.doxygen.nl/manual/docblocks.html
+[Markdown support]: http://www.doxygen.nl/manual/markdown.html
+[Formulas support]: http://www.doxygen.nl/manual/formulas.html
 [Supported formula commands]: http://docs.mathjax.org/en/latest/tex.html#supported-latex-commands
-[Command reference]: http://www.stack.nl/~dimitri/doxygen/manual/commands.html
+[Command reference]: http://www.doxygen.nl/manual/commands.html
 [Google Scholar]: http://scholar.google.ru/

doc/tutorials/introduction/windows_install/windows_install.markdown

@@ -151,7 +151,7 @@ of them, you need to download and install them on your system.
     image file format.
 -   The OpenNI Framework contains a set of open source APIs that provide support for natural interaction with devices via methods such as voice command recognition, hand gestures, and body
     motion tracking. Prebuilt binaries can be found [here](http://structure.io/openni). The source code of [OpenNI](https://github.com/OpenNI/OpenNI) and [OpenNI2](https://github.com/OpenNI/OpenNI2) are also available on Github.
--   [Doxygen](http://www.stack.nl/~dimitri/doxygen/) is a documentation generator and is the tool that will actually create the
+-   [Doxygen](http://www.doxygen.nl) is a documentation generator and is the tool that will actually create the
     *OpenCV documentation*.
 
 Now we will describe the steps to follow for a full build (using all the above frameworks, tools and