Add test virtual feature function. The running result is as follows:

	CBase::act1()! CBase::act2()! CBase::act3()! CBase::act4()! CBase::act5()!
	CBase::act5()!
	CBase::act1()! CBase::act2()! CDerive::act3()! CDerive::act4()! CDerive::act5()!
	CBase::act5()!

Signed-off-by: 瞿稻 <qudao@meizu.com>
可见，仍然调用的是子类的。
Signed-off-by: 瞿稻 <qudao@meizu.com>
Add constructor
Signed-off-by: 瞿稻 <qudao@meizu.com>