[cgo] Pointer variables are not implemented properly.

Pointer variables are making the headers not compile. We tried to use interface{} style-pointers in order to abstract this for the user, but they seemed to crash.

My suggestion would be to handle pointers strictly as uint64 handles throughout all the go code.
@qmuntal: Do you have any objections?

首先复现 issue 中描述的 header 编译失败，并跟踪 cgo 相关 Go 代码如何处理指针变量。将当前的 interface{} 风格指针处理与拟议的 uint64 句柄方案进行比较。完成的标准是生成的 header 能够编译，并且指针变量不再导致崩溃，但 issue 未指明任何文件或测试。

由索引模型根据 Issue 内容生成。