info/grafts: allow trailing whitespaces at the end of line

info/grafts: allow trailing whitespaces at the end of line

When creating an info/grafts under windows, one typically gets a CRLF file.
There is no good reason to forbid trailing CR at the end of the line (for
that matter, any trailing whitespaces); the code allowed only LF simply
because that was good enough for the platforms with LF line endings.

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