[XeTeX] can't access superscript glyphs outside Latin-1?

[Eric Abrahamsen]

I have an odd problem, and this is the only place I can think of to
bring it up.

I'm using XeLaTeX with fontspec and the Janson Pro OTF font from
Linotype. I noticed recently that I don't get many superscripts glyphs
when using "real" superscripts with \textsuperscript{} and xltxtra
loaded. Specifically, I could only get superscripts for 1, 2, and 3, and
"a" and "o", which seemed like a weird assortment.

Linotype assures me the other ones are in there. I notice that
superscripts for 1, 2, and 3 are all part of the Latin-1 block of
Unicode, and that the superscript-looking "a" and "o" are actually the
feminine and masculine ordinal indicators, also part of Latin-1.

So... I can't help but think that I'm not "accessing" glyphs from ranges
of codepoints outside Latin-1. I don't actually know all that much about
fonts in general or OTF fonts in particular, but I do have fontforge
installed on my machine and might be able to do something with it.

If it's relevant, I'm running archlinux and am using its TexLive 2012
package.

Can anyone give me any pointers?

Thanks!
Eric