Rename P4Ruby's P4DepotFile, P4Revision, and P4Integration classes
to be P4::DepotFile, P4::Revision and P4::Integration respectively.
Also changed P4Ruby's P4::Revision class to store arbitrary
attributes of revisions, which should help with server compatibility.
Note that P4Perl's already did that, so this just ports those changes
Also, changed the method name in P4Perl's class from
as that's a better name for it. P4Ruby's equivalent is called
User-visible change to be documented in Scripting Interfaces Guide