avoid (deprecated) Java.java_to_ruby use JavaUtil.convertJavaToRuby
when wrapping java.sql.Connection object into a Ruby object ...
re-arranged code to have code that sets connection on one place
add some (probably redundant) synchronization + arjdbc.disconnect.debug
for attempting to detect when connection is (closed and) set to null - this should be removed once #197 #198 are closed
prepare for 1.2.7