xsltproc never finishes (v1.1.33 regression)

Something changed between 1.1.32 and 1.1.33 that causes xsltproc to run forever (or at least longer than I care to wait) on a particular call.

Use the attached file test.xml and call

xsltproc -o out.fo http://docbook.sourceforge.net/release/xsl/1.79.1/fo/docbook.xsl test.xml

In older versions, this takes about 1 minute on my machine, or perhaps 2 minutes if the stylesheets need to be downloaded first. With 1.1.33 and master, this runs seemingly forever.

I bisected this down to this being the bad commit: a846514a

(We also use DocBook to build HTML and man pages, which works fine. So it's not completely broken, it's just something specific to this stylesheet.)