Documentation: Fix link to AppVeyor.
Sphinx linkcheck complains with:
Warning, treated as error:
.../Documentation/intro/install/windows.rst:1093:broken link:
www.appveyor.com ()
Add a https scheme in link to AppVeyor website.
@@ -1090,9 +1090,9 @@ To stop and delete the services, run:
Windows CI Service
------------------
-`AppVeyor <www.appveyor.com>`__ provides a free Windows autobuild service for
-open source projects. Open vSwitch has integration with AppVeyor for
-continuous build. A developer can build test his changes for Windows by
+`AppVeyor <https://www.appveyor.com>`__ provides a free Windows autobuild
+service for open source projects. Open vSwitch has integration with AppVeyor
+for continuous build. A developer can build test his changes for Windows by
logging into appveyor.com using a github account, creating a new project by
linking it to his development repository in github and triggering a new build.
