xml.el should ignore \r

[mah]

When parsing a file, xml.el should ignore \r.  Many XML sources
from the net contain this character.  See the source for
http://www.benhammersley.com/ for an example.

This means essentially replacing all "\t\n" in xml.el with
"\t\r\n", but I believe this should be a variable that can be
changed in just one spot (i.e. substitute "\t\n" with
xml-whitespace).

-- 
You are a mystery as deep as the sea; the more I search, the more
I find, and the more I find the more I search for you.
            -- St. Catherine of Siena