Update background keepalive pings:  - Fully lock the connection for background pings; this may slow down queries after connection disuse (when the keepalive is still active/blocked), but strengens thread safety to hopefully fix vio_delete crashes  - Fix pthread_cancel use; previously pthread_cancel after a keepalive may have resulted in cancelling unrelated threads where the thread ID was reused This should increase stability and improve program consistency.
Update background keepalive pings:
 - Fully lock the connection for background pings; this may slow down queries after connection disuse (when the keepalive is still active/blocked), but strengens thread safety to hopefully fix vio_delete crashes
 - Fix pthread_cancel use; previously pthread_cancel after a keepalive may have resulted in cancelling unrelated threads where the thread ID was reused
This should increase stability and improve program consistency.

prabowomurti/sequel-pro,Shooter7119/sequel-pro,vieten/sequel-pro,Shooter7119/sequel-pro,Shooter7119/sequel-pro,Shooter7119/sequel-pro,vieten/sequel-pro,vieten/sequel-pro,prabowomurti/sequel-pro,prabowomurti/sequel-pro,Shooter7119/sequel-pro,prabowomurti/sequel-pro,brittneybrinsfield/sequel-pro,prabowomurti/sequel-pro,brittneybrinsfield/sequel-pro,vieten/sequel-pro,brittneybrinsfield/sequel-pro,brittneybrinsfield/sequel-pro