Optimize SourceForge mirror

The current SourceForge mirror makes 5 redirects before reaching the final
URL. It will not work with less than 5

   $ mr=https://sourceforge.net/projects/msys2/files/REPOS/MSYS2/x86_64
   $ av=pacman-mirrors-20140201-1-any.pkg.tar.xz
   $ wget --spider --max-redirect 1 $mr/$av
   HTTP request sent, awaiting response... 301 Moved Permanently
   1 redirections exceeded.

A change in mirror can reduce the redirects to 1

   $ mr=http://downloads.sourceforge.net/project/msys2/REPOS/MSYS2/x86_64
   $ av=pacman-mirrors-20140201-1-any.pkg.tar.xz
   $ wget --spider --max-redirect 1 $mr/$av
   HTTP request sent, awaiting response... 200 OK
   Length: 1252 (1.2K) [application/octet-stream]
   Remote file exists.