Fix DBCP-347
Correct implementation of DelegatingStatement.isWrapperFor(). Also fix DelegatingDatabaseMetaData.isWrapperFor() and DelegatingResultSet.isWrapperFor() that had the same problem.
Based on a patch by Robert Poskrobek

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/dbcp/branches/DBCP_1_5_x_BRANCH@1549686 13f79535-47bb-0310-9956-ffa450edef68