[openbox] Only-non-iconics and only-iconics focus cyles patch

[Carlos Pita]

Some people (at least me) prefer to think of iconified windows as if
they were in a completely different focus cycle and not only pushed
down to the end of the current one. So I implemented this patch
https://bugzilla.icculus.org/show_bug.cgi?id=4876 that allows to
exclude iconified windows from the cycle, or inversely to restrict the
cycle to include just icons in order to restore them. This is
configured in a new child of Next/Previous Window actions:

<action name="NextWindow">
  <iconics>exclude</iconics>
</action>

where iconics is of type iconicmode declared as:

    <xsd:simpleType name="iconicmode">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="only"/>
            <xsd:enumeration value="include"/>
            <xsd:enumeration value="exclude"/>
        </xsd:restriction>
    </xsd:simpleType>

It's not well tested yet but it's simple enough to make me feel
somewhat confident about it.

Best regards
--
Carlos