Wrong validation of XML documents containing nested interleaves.

Tested against libxml2 version 2.9.1 in:
 * PHP 5.5 on Ubuntu 13.10,
 * Python with lxml on Ubuntu 13.10 and Cygwin.

Validation of XML documents using Relax NG schema containing nested interleaves gives incorrect results (in some cases).

Specifically using following test.rng schema all specified test.xml documents should be valid.
But <root><type>type2</type><tag/><tagY/></root> is incorrectly marked as invalid.

test.rng:
<element name="root" xmlns="http://relaxng.org/ns/structure/1.0">
    <interleave>
        <element name="tag"><empty/></element>
        <choice>
            <interleave>
                <element name="type"><value>type1</value></element>
                <element name="tagX"><empty/></element>
            </interleave>
            <interleave>
                <element name="type"><value>type2</value></element>
                <element name="tagY"><empty/></element>
            </interleave>
        </choice>
    </interleave>
</element>

test.xml:
<root><tag/><tagX/><type>type1</type></root> => document is valid
<root><tag/><tagY/><type>type2</type></root> => document is valid
<root><tag/><type>type1</type><tagX/></root> => document is valid
<root><tag/><type>type2</type><tagY/></root> => document is valid
<root><tagX/><tag/><type>type1</type></root> => document is valid
<root><tagX/><type>type1</type><tag/></root> => document is valid
<root><tagY/><tag/><type>type2</type></root> => document is valid
<root><tagY/><type>type2</type><tag/></root> => document is valid
<root><type>type1</type><tag/><tagX/></root> => document is valid
<root><type>type1</type><tagX/><tag/></root> => document is valid
<root><type>type2</type><tag/><tagY/></root> => document is **NOT** valid <- BUG
<root><type>type2</type><tagY/><tag/></root> => document is valid