Avoid terminating the PAM library in the forked child. This is done later

in the parent after closing the PAM session.
This fixes http://bugs.debian.org/412061.
Debian patch 405_su_no_pam_end_before_exec.

src/su.c

@@ -183,7 +183,12 @@ static void run_shell (const char *shellstr, char *args[], int doshell,
 
 	child = fork ();
 	if (child == 0) {	/* child shell */
-		pam_end (pamh, PAM_SUCCESS);
+		/*
+		 * PAM_DATA_SILENT is not supported by some modules, and
+		 * there is no strong need to clean up the process space's
+		 * memory since we will either call exec or exit.
+		pam_end (pamh, PAM_SUCCESS | PAM_DATA_SILENT);
+		 */
 
 		if (doshell)
 			(void) shell (shellstr, (char *) args[0], envp);