CrossTeX

Right now crosstex allows this (1):
\bibliography{foo,bar,baz}

but not this (2):
\bibliography{foo, bar, baz}

This behavior is backwards compatible with bibtex. Perhaps due to my coding
style, I usually end up putting spaces as in (2) and then I have to go back
and remove them because both crosstex and bibtex complain.

A one line fix resolves this issue, while still maintaining bibtex
compatibility. Patch attached (against svn trunk)