* src/pwck.c: Added fail_exit().

* src/pwck.c: Report failure to unlock files to stderr and
	syslog.
	* src/pwck.c: Report failure to sort to stderr, and exit with
	E_CANTSORT.
	* man/pwck.8.xml: Document return code 6 (E_CANTSORT).

man/pwck.8.xml

@@ -245,6 +245,12 @@
 	    <para>can't update password files</para>
 	  </listitem>
 	</varlistentry>
+	<varlistentry>
+	  <term><replaceable>6</replaceable></term>
+	  <listitem>
+	    <para>can't sort password files</para>
+	  </listitem>
+	</varlistentry>
       </variablelist>
     </para>
   </refsect1>