在调试一个程序时，将一个内存页面protect属性用VirtualProtectEx设置为PAGE_READONLY,
来实现当程序运行到该内存页面的地址范围时，产生中断。但是MSDN里对PAGE_READONLY却
说：
If the system differentiates between read-only access and execute access, an attempt to execute code in the committed region results in an access violation.
也就是说，按上面的方法可能有效，也可能无效。请问要怎样设置，才识使：
the system differentiates between read-only access and execute access？
