Expose AnyObjectId compareTo(byte[]) and compareTo(int[])

Storage systems can use these implementations to compare a passed
AnyObjectId with a stored representation of an ObjectId in the
canonical network byte order format.  This can be useful to do a
binary search, or just linear scan, over an encoded storage file.

Change-Id: I8c72993c4f4c6e98d599ac2c9867453752f25fd2
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>