Remove OpenGL viewport aligment restrictions.

Instead, take GL_PACK_ALIGNMENT into account when making screenshots.
This would allow fullscreen resolutions like 1366x768 without black bars.
Make local sounds full volume.

Prevents them from becoming spatialized when client entity number
dynamically changes.
Don't draw scroll thumb character shadow.
Fix software renderer compilation issue.
Fix video mode and geometry update for SDL 2.
Merge branch 'master' of https://github.com/AndreyNazarov/q2pro