Ensure that both Connection and XAConnection objects are closed. With Oracle, the XAConnection holds the physical database connection and a number of other caches which we need to release.
Merge remote-tracking branch 'btm/close-connections' into 3.0.0-Omnifone

Conflicts:
	btm/src/main/java/bitronix/tm/resource/jdbc/JdbcPooledConnection.java
	btm/src/main/java/bitronix/tm/resource/jms/JmsPooledConnection.java