[MONDRIAN-1819]  Mondrian generates timestamp predicates for date fields

This is an issue specific to the Oracle jdbc driver ojdbc5 and above, which treats the DATE datatype as a TIMESTAMP.  Because of this, dates can have a value like
'2001-01-19 00:00:00.0', which cannot be used as a DATE literal.  This change to OracleDialect.quoteDateLiteral() assures date literals conform to the ANSI spec.