Initial implementation of SUSP entries and Rock Ridge protocol

[dmchurch]

This is a fairly comprehensive implementation of SUSP, a mostly-complete implementation of RRIP, and a rudimentary integration into the existing isoparser structure. Features implemented:

• An extensible SUSP parser with full support for SUSP extensions, including proper extension name matching. Probably overkill; the Linux kernel itself doesn't bother matching extension IDs, it just assumes that no extensions will conflict with Rock Ridge. Which is probably a reasonable assumption.
• Support for the following Rock Ridge features: NM (alternate name), TF (file timestamps), SL (symlink targets), PX (posix stats), and PN (device major/minor).
• isofile.Record will now report the Rock Ridge name if available, and iso.record() will search on Rock Ridge names.

To do:

• Support more Rock Ridge properties in the Record class, especially symlink targets.
• Support deep directory hierarchies (the CL/PL/RE entries).

[barneygale]

Thanks very much for this. Do you have any HTTP-accessible ISOs you're using to test?

[dmchurch]

My primary use case is working with the Oracle Linux 7.2 ISO, which is available at https://mirrors.kernel.org/oracle/OL7/u2/x86_64/OracleLinux-R7-U2-Server-x86_64-dvd.iso