Compiling gdc : missing several headers : "cc.h".......etc

[Yuki]

Hello ,I am a new gdc user . I want to compile gdc 0.23's src with the 
mingw-gcc.But when compiling it. I find that some headers are missing. Could 
anyone tell me how to find those missing headers?.Are those headers gcc 
backend headers ? .Thanks.

#include "cc.h"
#include "el.h"
#include "oper.h"
#include "global.h"
#include "code.h"
#include "type.h"
and tassert.h..

Thanks.