htod - const

[dnewbie]

I have this file tmp.h:

const char *getvalue(const char *key);

I run htod tmp.h and I've got the output

-----------------------------------
/* Converted to D from tmp.h by htod */
module tmp;
//C     const char *getvalue(const char *key);
extern (C):
char * getvalue(char *key);
-----------------------------------

Why is 'const' removed?