src/passwd.c: inconsistent password length limit

The passwd utility had hardcoded limit for password lenght set
to 200 characters. In the agetpass.c is used PASS_MAX for
this purpose.

This patch moves the PASS_MAX definition to common place
and uses it in both places.

Signed-off-by: Tomas Halman <tomas@halman.net>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
Cherry-picked-from: f024002b3d66 ("src/passwd.c: inconsistent password length limit")
Cc: Serge Hallyn <serge@hallyn.com>
Link: <https://github.com/shadow-maint/shadow/pull/953>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/passwd.c

@@ -192,8 +192,8 @@ static int new_password (const struct passwd *pw)
 	char *cipher;		/* Pointer to cipher text */
 	const char *salt;	/* Pointer to new salt */
 	char *cp;		/* Pointer to agetpass() response */
-	char orig[200];		/* Original password */
-	char pass[200];		/* New password */
+	char orig[PASS_MAX + 1];	/* Original password */
+	char pass[PASS_MAX + 1];	/* New password */
 	int i;			/* Counter for retries */
 	bool warned;
 	int pass_max_len = -1;