* Need to update S4R.h to accommodate S-Plus 6 changes to the
  S4 API described in the green book.  In particular, I need to
  set 
     #define S_COMATIBILITY 10
  conditionally.  The problem is that there has to be an externally
  defined macro, say -DUSING_SPLUS=6|5 so that I can include either
  S.h or S_engine.h (as described in the S-Plus programmer's manual).
  This will probably kill any remaining hope of using this code 
  with Bell Labs' S4 implementation.

* [Done] Implement the "bind variables" idea -- useful for writing
  into databases, but not too critical(?) for select operations.

* [Done] Implement the "host arrays" feature that allows us to fetch
  multiple records per EXEC SQL FETCH.  This may give us a "markedly"
  performance (Ch 12, ProC/C++ manual).

* Security. Need to implement a better authentication mechanism,
  possibly similar to the MySQL or the ODBC?

* Performance. We haven't done anything on this yet.

* Long term. We should reimplement the guts to use OCI instead of
  the embedded ProC/C++.  A gentler (but not optimal) update would
  be to move to the ANSI dynamic embedded API available in Oracle
  since ~8.1.7(?) instead of the current Oracle-specific embedding
  approach (besides, it seems that the ANSI dynamic implementation
  doesn't have as many limitations as the API we're currently using).

* The RS-DBI needs to be finalized.  Once the R-SIG-DB agrees on
  a final API implement it. (We need to specify transactions, 
  asynchronous operations, bindings, security, connection pooling,
  etc.)

