adblock: update 3.4.1

adblock: update 3.4.1

* enable code to support Turris Omnia forthcoming upstream change
  (new kresd 'keep_cache' option) to preserve kresd DNS cache
* fix a 'status' race condition while the adblock process
  is running in parallel
* various small speed improvements
* rework debug output
* refine blacklist handling
* enable the (empty) blacklist source in the default config
* email notification supports mstmp, even without sendmail symlink
* email notification writes minimal status to log (one-liner)
* LuCI: refine logfile search term
* LuCI: Textarea 'autoscroll down' in logfile view
* LuCI: Left-align blocklist source table plus a more compact design

Signed-off-by: Dirk Brenken <dev@brenken.org>