attribute: whitespace set to true detects all errors known to git

attribute: whitespace set to true detects all errors known to git

That is what the documentation says, but the code pretends as if all the
known whitespace error tokens were given.

Among the whitespace error tokens, there is one kind that loosens the rule
when set: cr-at-eol.  Which means that whitespace error token that is set
to true ignores a newly introduced CR at the end, which is inconsistent
with the documentation.

Signed-off-by: Junio C Hamano <gitster@pobox.com>