Enhance ovbackup format to detect restore on different arch or GT.M version

Currently, a backup file generated by ovbackup contains a global directory, a database file, and routine files. Unfortunately, the global directory is architecture and GT.M-version specific (or at least can be), and the database file can also be GT.M-version specific.

At a minimum, we should store the architecture and GT.M version that a backup file was generated with so that we can prevent a user from restoring the backup if it won't restore correctly on their version of GT.M. Ideally, if the difference can easily be accounted for (by running a mupip upgrade, for example), we would just do the upgrade on-the-fly during the restore.