Use #include "windows" (lowercase 'w') to support crosscompilation e.g. on mingw64 on Ubuntu (#81, thanks @geghamyan variant-lite PR 57)

Author: martinmoene

include/lest/lest_cpp03.hpp

@@ -66,7 +66,7 @@
 #if lest_FEATURE_TIME
 # if lest_PLATFORM_IS_WINDOWS
 #  include <iomanip>
-#  include <Windows.h>
+#  include <windows.h>
 # else
 #  include <iomanip>
 #  include <sys/time.h>