Updating JAVASTACKTRACEPART to recognise native methods and methods with numbers.

For example:
        at sun.nio.ch.FileDispatcherImpl.read0(Native Method)

This does not have a filename or line number, and the method name
'read0' does not match the WORD pattern.

Another example:

        at kafka.server.KafkaApis.kafka$server$KafkaApis$$readMessageSets(KafkaApis.scala:380)

The method name here again does not mach the WORD pattern.