When a table was explicitly locked with LOCK TABLES no associated
tables from any related trigger on the subject table were locked.
As a result of this the user could experience unexpected locking
behavior and statement failures similar to "failed: 1100: Table'xx'
was not locked with LOCK TABLES".

This patch fixes this problem by making sure triggers are
pre-loaded on any statement if the subject table was explicitly
locked with LOCK TABLES.


mysql-test/r/sp-prelocking.result:
  Added test case
mysql-test/t/sp-prelocking.test:
  Added test case
sql/sql_lex.cc:
  - Moved some conditional logic out of the table iteration.
  - Added event map values for LOCK TABLE command.
sql/table.cc:
  - Refactored set_trg_event_tpye into the two simpler functions set_trg_event_map
    and set_trg_event_map as methods for manipulating the table event map.
    The original function was only called from st_lex::set_trg_event_type_for_tables
    so it was possible to move the event map creation logic to this function as
    a loop optimization.
sql/table.h:
  - Refactored set_trg_event_tpye into the two simpler functions set_trg_event_map
    and set_trg_event_map as methods for manipulating the table event map.
    The original function was only called from st_lex::set_trg_event_type_for_tables
    so it was possible to move the event map creation logic to this function as
    a loop optimization.