[XeTeX] Minor updates to fontspec and xltxtra

[Will Robertson]

Hello,

Hopefully this will be the last time I think about these two packages  
for a while. I've fixed up a couple of problems in both of them and  
they're on their way to CTAN. And of course they're also available  
through the SVN repository if you like to get things that way.

Changes:

xltxtra - Jonathan pointed out an egregious flaw in the package that  
made logos look TERRIBLE if they weren't at \normalsize. Oops!

fontspec - no longer crashes hard if you use \addfontfeature  
inappropriately
          - added a couple more maths packages to the list to not  
mess around with the maths
            (MinionPro and something else, I think)

Hopefully nothing turns out poorly! (Except that the documentation  
for fontspec will be a few days out of date (and the typeset  
implementation missing a couple of minor changes to the dtx.)

Well, that's two tasks off my list...

Cheers,
Will