CONNECTED-DATABASES — Return the list of active database objects.
Function
This function returns the list of active database
	  objects, i.e. all those database objects created by calls to 
	  connect, which have not been closed by
	  calling disconnect on them.
The consequences of modifying the list returned by
	    connected-databases are
	    undefined.
(connected-databases)
=> NIL
(connect '(nil "template1" "dent" nil) :database-type :postgresql)
=> #<CLSQL-POSTGRESQL:POSTGRESQL-DATABASE {4830BC65}>
(connect '("dent" "newesim" "dent" "dent") :database-type :mysql)
=> #<CLSQL-MYSQL:MYSQL-DATABASE {4830C5AD}>
(connected-databases)
=> (#<CLSQL-MYSQL:MYSQL-DATABASE {4830C5AD}>
    #<CLSQL-POSTGRESQL:POSTGRESQL-DATABASE {4830BC65}>)
(disconnect)
=> T
(connected-databases)
=> (#<CLSQL-POSTGRESQL:POSTGRESQL-DATABASE {4830BC65}>)
(disconnect)
=> T
(connected-databases)
=> NIL