Add following to chpasswd.c just after #include statements. All error will vanish, and compilation will succeeded.
void getword(char *word, char *line, char stop);
void Herror(char *msg, FILE * fpw, FILE * tmp);
void putline(FILE *,char *);
void Hmsg(char *msg);
void sendmail(char *user, char *subj, char *msg);
void Herror(char *msg, FILE * fpw, FILE * tmp);
void Changed(char *user, char *PwdLogFile, char *newpwd, char *showpwd, char *Pw
dFile, char *SmtpUser, char *SmtpSubject);
void NotFound(char *user, char *PwdLogFile, char *newpwd, char *showpwd, char *P
wdFile, char *SmtpUser, char *SmtpSubject);
void rulefail(char *minchar, char *minnum, char *minspec);
static void strip_latin(char *line);
