Replace mh_xmalloc() with mh_xcalloc()

[mmh] / h / utils.h

/*
** utils.h -- utility prototypes
*/

void *mh_xrealloc(void *, size_t);
void *mh_xcalloc(size_t, size_t);
char *pwd(void);
char *add(char *, char *);
void create_folder(char *, int, void (*)(int));
int num_digits(int);

struct msgs_array {
        int max, size;
        char **msgs;
};

void app_msgarg(struct msgs_array *, char *);