useradd/usermod: add --selinux-range argument

Add a command line argument to useradd(8) and usermod(8) to specify the
MLS range for a SELinux user mapping.

Improves: #676

man/usermod.8.xml

@@ -510,6 +510,23 @@
 	  </para>
 	</listitem>
       </varlistentry>
+      <varlistentry>
+	<term>
+	  <option>--selinux-range</option>&nbsp;<replaceable>SERANGE</replaceable>
+	</term>
+	<listitem>
+	  <para>
+	    defines the SELinux MLS range for the new account.
+	    Note that the shadow system doesn't store the selinux-range,
+	    it uses <citerefentry><refentrytitle>semanage</refentrytitle>
+	    <manvolnum>8</manvolnum></citerefentry> for that.
+	  </para>
+	  <para>
+	    This option is only valid if the <option>-Z</option> (or
+	    <option>--selinux-user</option>) option is specified.
+	  </para>
+	</listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>