Auto generate config header using Clang AST

#include "config.h"

int   REG_A     = 10;
float REG_B     = 10;
int   REG_C[10] = {0};

extern int   REG_A;
extern float REG_B;
extern int   REG_C[10];

Clang 真是好玩的東西，可以自己寫 compiler 拉~~~哈哈哈哈