test against __WINDOWS__ not __WIN32__

__WIN32__ was defined by MinGW though
Merge pull request #305 from pijyoi/win32_ctrlc

test against __WINDOWS__ not __WIN32__
add additional test for zsys_vprintf exposing bug in implementation
Merge pull request #304 from hintjens/master

Minor project cleanups
Merge pull request #306 from pijyoi/master

add additional test for zsys_vprintf exposing bug in implementation
Fixed issue #307