Call NULL by its name

In variadic functions we still do the cast.  In POSIX, it's not
necessary, since NULL is required to be of type 'void *', and 'void *'
is guaranteed to have the same alignment and representation as 'char *'.
However, since ISO C still doesn't mandate that, and moreover they're
doing dubious stuff by adding nullptr, let's be on the cautious side.
Also, C++ requires that NULL is _not_ 'void *', but either plain 0 or
some magic stuff.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

libmisc/entry.c

@@ -24,7 +24,7 @@ void pw_entry (const char *name, struct passwd *pwent)
 	struct spwd *spwd;
 
 	if (!(passwd = getpwnam (name))) { /* local, no need for xgetpwnam */
-		pwent->pw_name = (char *) 0;
+		pwent->pw_name = NULL;
 		return;
 	} else {
 		pwent->pw_name = xstrdup (passwd->pw_name);