This package was previously used to provide a number of features that were
useful for typesetting documents with XeLaTeX. Many of those features have now
been incorporated into the fontspec package and other packages, but the package
persists for backwards compatibility. Nowadays, loading xltxtra will: load the
fontspec, metalogo, and realscripts packages; redefine \showhyphens so it works
correctly; and define two extra commands: \vfrac and \namedglyph.
