Add new P4#tagged() method, that takes a bool, and a block.
It sets/clears
tagged output (as specified by the boolean), and runs the block. It then
resets the tagged output to its previous value. For example
This is in fact the best use-case, since getting a counter value is
harder in tagged mode than in non-tagged mode. Most users
will not need this method.
User-visible enhancement documented in p4rubynotes.txt