#5860 "Multi-table UPDATE does not activate update triggers"
 #6812 "Triggers are not activated for INSERT ... SELECT"
 #8755 "Trigger is not activated by LOAD DATA".
This patch also implements proper handling of triggers for special forms
of insert like REPLACE or INSERT ... ON DUPLICATE KEY UPDATE. 
Also now we don't call after trigger in case when we have failed to
inserted/update or delete row. Trigger failure should stop statement
execution.

I have not properly tested handling of errors which happen inside of
triggers in this patch, since it is simplier to do this once we will be
able to access tables from triggers.