Do not use SQL states for exceptions in jdbc/sqlanywhere adapter

The sqlanywhere JDBC driver (or SQLAnywhere itself) has broken
SQL State handling, using 23000 for most constraint exceptions.
Changes made in 813db79 to
make the jdbc adapter consider SQL states of the current
exception resulted in the use of SQL states in the
jdbc/sqlanywhere, where they didn't work correctly.  Explicitly
mark the jdbc/sqlanywhere adapter to not handle SQL states.
The shared sqlanywhere adapter handles the exception mapping
correctly in this case.

lib/sequel/adapters/jdbc/sqlanywhere.rb

@@ -36,6 +36,10 @@ module DatabaseMethods
 
         private
 
+        def database_exception_use_sqlstates?
+          false
+        end
+
         # Use @@IDENTITY to get the last inserted id
         def last_insert_id(conn, opts=OPTS)
           statement(conn) do |stmt|