doom-wad: Add .rts extension
Skyroads: Mark roads subfiles as not-compressed

This is because the files aren't compressed in full, just the last part
of the file is compressed so this should be handled in the map reader
rather than the archive reader.
Change test code to print proper hex dump on output content mismatch
Allow isInstance to flag other files as misdetections of self

This isn't yet used, but is being added for consistency with the test code for
the other Camoto libraries.