Rixed runtime casting problem when using sqlline/lingua

Was getting this odd stacktrace even though compile was clean. Having both method signatures available seems to fix the issue. Since the calls in OptiqDatabaseMetaData needs to do doing OptiqConnectionImpl specific operations the double-signature seems less silly than repeated casting.

0: jdbc:lingual:local> select * from EMPLOYEES.DEPARTMENTS ;
2013-06-11 10:53:05,386 INFO  [main] jdbc.LingualStatement (LingualStatement.java:execute(210)) - execute: select * from EMPLOYEES.DEPARTMENTS
java.lang.NoSuchMethodError: net.hydromatic.optiq.jdbc.Helper.createEmptyResultSet(Lnet/hydromatic/optiq/jdbc/OptiqConnectionImpl;)Ljava/sql/ResultSet;
	at net.hydromatic.optiq.jdbc.OptiqDatabaseMetaData.getPrimaryKeys(OptiqDatabaseMetaData.java:590)
	at cascading.lingual.jdbc.LingualDatabaseMetaData.getPrimaryKeys(LingualDatabaseMetaData.java:838)
	at sqlline.SqlLine$Rows.isPrimaryKey(SqlLine.java:2389)
	at sqlline.SqlLine$TableOutputFormat.getOutputString(SqlLine.java:2301)
	at sqlline.SqlLine$TableOutputFormat.getOutputString(SqlLine.java:2285)
	at sqlline.SqlLine$TableOutputFormat.print(SqlLine.java:2232)
	at sqlline.SqlLine.print(SqlLine.java:1889)
	at sqlline.SqlLine$Commands.execute(SqlLine.java:3837)
	at sqlline.SqlLine$Commands.sql(SqlLine.java:3738)
	at sqlline.SqlLine.dispatch(SqlLine.java:882)
	at sqlline.SqlLine.begin(SqlLine.java:717)
	at sqlline.SqlLine.mainWithInputRedirection(SqlLine.java:460)
	at sqlline.SqlLine.main(SqlLine.java:443)
	at cascading.lingual.shell.Shell.handle(Shell.java:147)
	at cascading.lingual.shell.Shell.execute(Shell.java:68)
	at cascading.lingual.shell.Shell.main(Shell.java:47)