convert: The native line-ending is \r\n on MinGW

If you try this: 1. Install Git for Windows (from the msysgit project) 2. Put [core] autocrlf = false eol = native in your .gitconfig. 3. Clone a project with *.txt text in its .gitattributes. Then with current git, any text files checked out have LF line endings, instead of the expected CRLF. Cc: Johannes Schindelin <johannes.schindelin@gmx.de> Cc: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>