SERVER-9580 Fixed problem with sleepmillis() on Windows due to default timer resolution being typically higher than 15ms

All sleepmillis() calls with values lesser than timer resolution will sleep AT LEAST the timer resolution value, making Mongo be really slow on certain use cases. Like when implementing consumer/producer patterns using capped collections to stream objects back and forth
@benety , I will try to use the header. I leave it up to you guys, but surely that will bring a bunch of other unnecessary declarations and I doubt MS changes in the future the prototype of this function. Apparently it's a very old API.