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 , if you prefer include header file, please let me know which one. only one I know will get this for sure is <windows.h>, but that will be huge inclusion and I didn't see it already included anywhere in the file, that's why I tried to avoid it.