Just to make sure you're aware of this, FC4 (x86_64) build fails: http://fedoraproject.org/extras/development/build-logs/x86_64/perl-XML-LibXSLT-1.57-3.log
looks like i386 died also... :P tests succeed in a recent local mach i386 build root (probably libxml2-2.6.19 fixed the invalid pointer?). requesting rebuild in wiki. upstream notified of gcc4 warnings.
FYI, I tested downgrading libxml2 to 2.6.17-6 included in FC4t1 and rebuilt this on i386 -> success, ditto with 2.6.19. It's of course possible that whatever is fixed in libxml2 2.6.19 affects x86_64 only, we'll see.
build passed.