DBCP-380
Correct implementation of DelegatingConnection.isWrapperFor() so it works correctly with older JDBC drivers.
Patch provided by Balazs Zsoldos.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/dbcp/branches/DBCP_1_5_x_BRANCH@1549678 13f79535-47bb-0310-9956-ffa450edef68