[Pmt-exif] HEX syntax

[Glenn Randers-P. <gl...@ho...>]

I think we need to say something about the "endian" condition of data
stored in a HEX string.  The HEX data is simply copied from a TIFF/EP tag
as is, and therefore uses the same endian style as the camera uses.

One possibility is to require applications to write a
PNG_ByteOrder subkeyword (value 0: unknown, 1: BigEndian, 2: LittleEndian)
if they plan to write HEX that contains multibyte entities.

Glenn