Support suppressed exceptions in log formatting

In JDK 7 and on, a Throwable bundles a list of suppressed exceptions. We should be logging these as part of our exception formatting... however we have to do so thoughtfully, because every caused-by and suppressed exception may in turn have more suppressed exceptions and caused-by.

This JIRA was created to track a back port of the JDK 7 enhancement to support suppressed exceptions to the 1.5.x branch which requires JDK 6. This will introduce a new requirement that the 1.5 branch will require JDK 7 to compile, but will still work on JDK 6.