Code review comment for ~bhill/epics-base:db-tpro-show-values

Core Meeting: Should be done for (and messages consistent from) all record types; TPRO value of 1 should be reserved for just the current trace processing, values for these messages should be sensible (higher numbers may print more stuff, leave room between numbers for device support, link support etc. to use as well); consider adding another message when beginning/ending an asynchronous I/O operation.