so we've got this patch to libxml2 2.7.6 in the LibreOffice code base,
inherited from OOo.  it fixes a definite problem, which is that Windows
has a rather low maximum path length restriction, and there is a special
trick on NT whereby path names can be prefixed with "\\?\", in which
case the maximum length is 32k, which ought to be sufficient even for
bloated office suites :)

I'll attach the patch to the xmlCanonicPath function.  note that i
didn't write this and am by no means an expert on either Microsoftean
platforms or libxml so maybe it's not the best way to do it.