*Cube Gears:
Added glDepthMask (GL_TRUE); and glDepthFunc (GL_LESS); to void
GearsScreen::cubePaintInside (...) to fix the culling on multimonitor
systems (green gear was always rendered in front).
Also fixed indentation and removed some redundant newlines.
(LP: #1168919). Fixes: https://bugs.launchpad.net/bugs/1168919.
Approved by PS Jenkins bot, Sam Spilsbury.