Provided Basic Support for -l N option on windows platform.

I have implemented basic support for **-l N** on windows platform.

Tested with platform==msvc and platform==mingw.

Values returned from OS are filtered with basic filter, to minimize load variation caused by short time between consecutive calls.

I have tested it on 2 core machine with HT and 4 core one, and CPU load in Task Manager matches one provided in -l option.

Any suggestion and improvements are moe than welcome.


`-` so `previous load` would be negative, and so will be `load` returned on first call. This will allow first call to be interpreted as error by caller.

There were multiple `f` added to double constants in other parts of file (like in POSIX GetLoadAverge). Can I fix `f `s introduced by me now (and maybe rest of them another time)?