Fix incorrect use of variable arguments in run_parts() and simplify code

The run_parts() implementation used variable arguments in a bad way,
resulting in it not working properly.  Replaced va_*() code with a
simple cmd argument that's passed to each script called.

Also, the opendir()/readdir() code has been replaced with scandir()
using regular alphasort(). This simplifies the code somewhat as well.

Otherwise, minor cleanups.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

fmode.c

@@ -39,7 +39,7 @@ mode_t fmode(char *file)
 
 	if (!file) {
 		errno = EINVAL;
-		return 0;	/* Doesn't exist ... */
+		return 0;
 	}
 
 	if (!stat(file, &sb))