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.


While statics will be initialized on first function call, I would prefer not to depend on this bahavior, as current version is readable event without being aware of that.

Besides, it will not be branch free - I cannot return 0 when `totalTicksSinceLastTime ` is 0, because `GetSystemTimes` called too often can return previous result. For sample build it happens quite often, so for example every second call would return 0 then.

I created sample program calling GetAvaregaLoad 1e6 times in a loop, and get from 100 to 2000 consecutive readouts with same values. On actual build it was around 2-3 same readouts during consecutive calls.