XML processing instructions with embedded '>' fail to parse

[toddlipcon]

Commit 7e54bff broke the parsing of multi-line XML processing instructions. For example, the following valid XML file:

<?xml version="1.0" encoding="UTF-8"?>
<project>
  <?pi <tag>
    </tag>
  ?>
</project>

throws:
org.codehaus.plexus.util.xml.pull.XmlPullParserException: processing instruction started on line 2 and column 5 was not closed (position: TEXT seen ...\n <?pi\n ... @3:9)

This causes Maven 3.6 (which uses plexus-interpolation 1.25) to fail to parse some poms which use a multi-line processing instruction as an "ignore" block.

[toddlipcon]

Turns out it's not multi-line that's an issue, but rather the inclusion of a '>' in the PI content (which is allowed by the XML spec best I can tell)