xdoxslt:chr() function not supported

I'm posting this here so that if someone else ends up beating their head against this issue, they can hopefully find it and save themselves some time. 

"According to the core team confirmation the Oracle BI Publisher functionality does not support the xdoxslt:chr() function and has no intention of supporting it."

That's a direct quote from the support analyst.  That said, some usages of xdoxslt:chr() do seem to work, so you'll just have to test it.