On windows, unless we use the O_BINARY flag in the open()
call, the file I/O routines will perform line ending
conversion (\r\n => \n on input, \n => \r\n on output).
In addition to the performance penalty, most files in the
object database are binary and will, therefore, become
corrupted by this conversion.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>