1. Special mode to search in error logs: if SEARCH_RANGE is not set,
the file is considered an error log and the search is performed
since the last CURRENT_TEST: line
2. Number of matches is printed too. "FOUND 5 /foo/ in bar".
Use greedy .* at the end of the pattern if number of matches
isn't stable. If nothing is found it's still "NOT FOUND",
not "FOUND 0".
3. SEARCH_ABORT specifies the prefix of the output.
Can be "NOT FOUND" or "FOUND" as before,
but also "FOUND 5 " if needed.
There is a race condition during shutdown, that happens when "show status" runs during shutdown.
Functions show_slave_running(), show_slave_received_heartbeats(), show_heartbeat_period() would dereference NULL pointer master_info_index, after this variable is set to NULL in slave_end() during shutdown.
Fix introduces check for master_info_index == NULL in the affected functions.
