We had changed that once before in the other direction in svn r421
Reason back then was "Sleep(0) doesn't allow any lower priority threads to execute"
But Microsoft changed the behaviour of Sleep(0) after Windows XP so that's no longer true.
And the costs of it is pretty high - due to this using a timer with a 15ms resolutions it meant not just giving up the thread but it also always waited for 15ms on Windows.
I also replaced a few sleep calls in examples for that reason with yield() calls.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6459 dfc29bdd-3216-0410-991c-e03cc46cb475
