Add FindWindowEx about win HOT 2 OPEN

example:
// StringToUTF16PtrElseNil String To UTF16Ptr if empty string trans to nil
func StringToUTF16PtrElseNil(str string) *uint16 {
if str == "" {
return nil
}
return syscall.StringToUTF16Ptr(str)
}

// FindWindow find window hwnd by name class="" if nil,nil mean ignore it
func FindWindow(class, title string) win.HWND {
var hwnd win.HWND
hwnd = win.FindWindow(StringToUTF16PtrElseNil(class), StringToUTF16PtrElseNil(title))
return hwnd
}

// FindWindowEx find window hwnd by name class="" if nil,nil mean ignore it
func FindWindowEx(hWndParent, hWndChild win.HWND, class, title string) win.HWND {
var hwnd win.HWND
hwnd = win.FindWindowEx(hWndParent, hWndChild,
StringToUTF16PtrElseNil(class),
StringToUTF16PtrElseNil(title))
return hwnd
}

from win.

// FindWindowEx find window hwnd by name class="" if nil,nil mean ignore it 这个注释要更新一下

from win.