Bug#696649: Solution/workaround

[Pietro Battiston]

I was also hit by this bug when upgrading to 3.8. The two possible
solutions are:
1) switch to the "Super" key, which is now the default modifier for most
window-related actions,
2) install gnome-tweak-tools and change such modifer (in the "Windows"
section).

Since this is clearly a design choice, it will probably never be
"fixed", so I think the bug can be closed.

Sources:
http://superuser.com/questions/428974/how-to-enable-dragging-windows-with-alt-click-in-gnome-3-gnome-shell
(answers by Scott and Pelle, _not_ the obsolete one by janos), and
http://www.ryanlerch.org/blog/alt-click-drag-to-move-windows-no-longer-works-in-fedora-18-gnome-3-8/