Convert .rpm files for extraction with /usr/bin/cpio

Quoting the author:

why does the world need another rpm2cpio?  because the existing one
won't build unless you have half a ton of things that aren't really
required for it, since it uses the same library used to extract RPM's.
in particular, it won't build on the HPsUX box I'm on.

(this one needs just perl)

Updated version by Sergey Babkin that doesn't slurp the entire file
into memory and supports the newer bzip2 compressed rpms.

BUGS: if the rpm contains more than one cpio file this version
extracts only the first one. (I don't know how widespread these
types of rpms are, i haven't yet seen one.  If you do, try the
binary rpm2cpio that comes with the archivers/rpm port.)

Now called rpm2cpio.pl so that it doesn't conflict with the binary one.