gears.cpp, gears.h:
Do not render the gears if we are viewing the cube from the inside -
the gears are otherwise obstructing the users' view on his workspaces.
Print a warning to the console once in this case.
(LP: #1185819). Fixes: https://bugs.launchpad.net/bugs/1185819.
Approved by Sam Spilsbury, PS Jenkins bot.