[XeTeX] how to create and install xexmltex.fmt

[Arthur Reutenauer]

> Provided that you will set only Greek and English text. 

  That's not the problem: the issue is with the hyphenation patterns
that are loaded are format generation time; if William has installed the
full set of languages he has dozens of them, in various writing systems.
He should really use unicode-letters.tex that has been devised for that
exact purpose.

  The cleanest way is probably to have a copy of xelatex.ini named
xexmltex.ini, that loads xmltex.tex in addition; this way one can
benefit from all the other settings that are done there (loading
unicode-letters is only one of them).

	Arthur