Windows implementation.

[ssrlive]

This is windows implementation for coroutine, fully tested.

d:\coroutine\build>debug\demo.exe
main start
coroutine 1 : 0
coroutine 2 : 100
coroutine 1 : 1
coroutine 2 : 101
coroutine 1 : 2
coroutine 2 : 102
coroutine 1 : 3
coroutine 2 : 103
coroutine 1 : 4
coroutine 2 : 104
main end