Update broken downloads link in documentation (#8764)

* Update broken downloads link

* Update broken downloads link

* Update broken downloads link

doc/tutorials/introduction/building_tegra_cuda/building_tegra_cuda.markdown

@@ -29,7 +29,7 @@ Getting the Source Code {#tutorial_building_tegra_cuda_getting_the_code}
 
 There are two (2) ways to get the OpenCV source code:
 
-* Direct download from the [OpenCV downloads](http://opencv.org/downloads.html) page
+* Direct download from the [OpenCV downloads](http://opencv.org/releases.html) page
 * Cloning the git repositories hosted on [GitHub](https://github.com/opencv)
 
 For this guide, the focus is on using the git repositories. This is because the 3.1.0 version of OpenCV will not build with CUDA 8.0 without applying a few small upstream changes from the git repository.

doc/tutorials/introduction/java_eclipse/java_eclipse.markdown

@@ -10,7 +10,7 @@ less mistakes. Here we go.
 Configuring Eclipse
 -------------------
 
-First, obtain a fresh release of OpenCV [from download page](http://opencv.org/downloads.html) and
+First, obtain a fresh release of OpenCV [from download page](http://opencv.org/releases.html) and
 extract it under a simple location like `C:\OpenCV-2.4.6\`. I am using version 2.4.6, but the steps
 are more or less the same for other versions.
 

doc/tutorials/introduction/linux_install/linux_install.markdown

@@ -33,7 +33,7 @@ repository](https://github.com/opencv/opencv.git).
 
 ### Getting the Latest Stable OpenCV Version
 
--   Go to our [downloads page](http://opencv.org/downloads.html).
+-   Go to our [downloads page](http://opencv.org/releases.html).
 -   Download the source archive and unpack it.
 
 ### Getting the Cutting-edge OpenCV from the Git Repository