main.c: Use ISO C99-compatible declaration for main

C99 §5.1.2.2.1 only defines the following declarations for main:

- int main(void)
- int main(int argc, char *argv[])

While the use of equivalent types (e.g.: char **argv) is allowed, const
char ** would not be considered equivalent, and thus an invalid
declaration depending on the implementation.

main.c

@@ -1424,7 +1424,7 @@ end:
     return ret;
 }
 
-int main(const int argc, char *const argv[])
+int main(int argc, char *argv[])
 {
     int ret = EXIT_FAILURE;
     struct handler *h = NULL;