Fix recursion accounting in XPath expressions:

  https://gitlab.gnome.org/GNOME/libxml2/-/issues/264

Taken from upstream:

  https://gitlab.gnome.org/GNOME/libxml2/-/commit/3e1aad4fe584747fd7d17cc7b2863a78e2d21a77

diff --git a/xpath.c b/xpath.c
--- a/xpath.c
+++ b/xpath.c
@@ -10983,7 +10983,7 @@ xmlXPathCompileExpr(xmlXPathParserContextPtr ctxt, int sort) {
     }
 
     if (xpctxt != NULL)
-        xpctxt->depth -= 1;
+        xpctxt->depth -= 10;
 }
 
 /**
d class='main'><a href='/'>index</a> : <a href='/guix/'>guix</a></td><td class='form'><form method='get'>
<input type='hidden' name='id' value='cf8e55f0ab0f9550f19aca0fea349f8a386ac595'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>refs</a><a class='active' href='/guix/log/etc/copyright.el'>log</a><a href='/guix/tree/etc/copyright.el?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>tree</a><a href='/guix/commit/etc/copyright.el?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>commit</a><a href='/guix/diff/etc/copyright.el?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/etc/copyright.el'>
<input type='hidden' name='id' value='cf8e55f0ab0f9550f19aca0fea349f8a386ac595'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>root</a>/<a href='/guix/log/etc?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>etc</a>/<a href='/guix/log/etc/copyright.el?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595'>copyright.el</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/copyright.el?id=cf8e55f0ab0f9550f19aca0fea349f8a386ac595&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-02-22 17:56:31 +0300'>2020-02-22</span></td><td><a href='/guix/commit/etc/copyright.el?id=9a3971143854bf877c0739fc8fdf7b945a2e3935'>etc: Add copyright.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/copyright.el: New file.
* doc/contributing.texi (The Perfect Setup): Document this.
</span></span></td><td>Oleg Pykhalov</td></tr>