Brief Description of Design and Flow of Code:
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The interface for the sql interface is described in 
sql-interface.h:Sql_interface :

// This is the 'interface' that each database class has to provide.
// Inherit from this class in your database class and provide all
// of the functions listed here.


This implementation of this interface for MySQL is 
in files sql-mysql.{h,cxx} .


sql.cc contains the the functions for connecting from Sql_interface
to Tcl. Each 'sql' command has a corresponding implementation here.
These functions handle the transport of data to and from Tcl; no
code for direct interaction with the database is found in this file.


sql-manager.{h,cxx} implement the management classes for connections
to the database. The 'Manager_sql' manages which connections are
free and which are in use.

