We were using md5_hex to generate a unique file id from a full path
filename. Changed this to use the file device and inode id instead.
Should still provide unique file ids and the file names are shorter
too.
Fixes#29
Changed all header file once include variables to follow the same naming
convention and not start with any underscores. Also deleted old
incorrect copyright notices. Also removed $Id: tags from all files.
Fixes#14. Fixes#22.