Recovering the build process after adding fields to the engine.

The following steps were used in Win32, but the idea may apply to other platforms
as well. This solution implies manual intervention. Permanent changes were
suggested in fb-devel that allow an automated build to succeed.

- Start the current build's executable (let's assume the debug server).
- Modify preprocess.bat as instructed inside the file (look for "CVC -" comments).
The problem lies mainly with backup.epp and restore.epp, both part of gbak.
- Run make_boot for release and make_all for release. This step must catch
compilation errors. The idea is to avoid the build process getting rid of the
current debug server version. If only build_all has problems, keep running
preprocess.bat after your changes and then build_all until everything compiles.
- Run make_boot for debug.
- Shutdown the server.
- Run make_all for debug.
- Start the newly compiled server instance (debug or release, although
debug will catch more problems. We'll assume the debug server).
- Run prepare with the path pointing to the running server's root dir. Now you
have the build support databases (gen/dbs) with the new structure.
- Revert preprocess.bat to the normal state (undo the temporary changes).
- Run make_boot for release and make_all for release.
- Run make_boot for debug.
- Shutdown the server.
- Run make_all for debug.

You should have the server, the utilities and the support databases with the
changed structure. Now both the release and debug versions are upgraded.

