MDEV-6112 multiple triggers per table

This is similar to MysQL Worklog 3253, but with
a different implementation. The disk format and
SQL syntax is identical with MySQL 5.7.

Fetures supported:
- "Any" ammount of any trigger
- Supports FOLLOWS and PRECEDES to be
  able to put triggers in a certain execution order.

Implementation details:
- Class Trigger added to hold information about a trigger.
  Before this trigger information was stored in a set of lists in
  Table_triggers_list and in Table_triggers_list::bodies
- Each Trigger has a next field that poinst to the next Trigger with the
  same action and time.
- When accessing a trigger, we now always access all linked triggers
- The list are now only used to load and save trigger files.
- MySQL trigger test case (trigger_wl3253) added and we execute these
  identically.
- Even more gracefully handling of wrong trigger files than before. This
  is useful if a trigger file uses functions or syntax not provided by
  the server.
- Each trigger now has a "Created" field that shows when the trigger was
  created, with 2 decimals.

Other comments:
- Many of the changes in test files was done because of the new "Created"
  field in the trigger file. This shows up in SHOW ... TRIGGER and when
  using information_schema.trigger.
- Don't check if all memory is released if on uses --gdb;  This is needed
  to be able to get a list from safemalloc of not freed memory while
  debugging.
- Added option to trim_whitespace() to know how many prefix characters
  was skipped.
- Changed a few ulonglong sql_mode to sql_mode_t, to find some wrong usage
  of sql_mode.

mysql-test/r/mysqlcheck.result

@@ -241,15 +241,15 @@ CREATE TABLE t1 (a INT) engine=myisam;
 SELECT * FROM INFORMATION_SCHEMA.TRIGGERS
 WHERE TRIGGER_SCHEMA="#mysql50#a@b" ORDER BY trigger_name;
 TRIGGER_CATALOG	TRIGGER_SCHEMA	TRIGGER_NAME	EVENT_MANIPULATION	EVENT_OBJECT_CATALOG	EVENT_OBJECT_SCHEMA	EVENT_OBJECT_TABLE	ACTION_ORDER	ACTION_CONDITION	ACTION_STATEMENT	ACTION_ORIENTATION	ACTION_TIMING	ACTION_REFERENCE_OLD_TABLE	ACTION_REFERENCE_NEW_TABLE	ACTION_REFERENCE_OLD_ROW	ACTION_REFERENCE_NEW_ROW	CREATED	SQL_MODE	DEFINER	CHARACTER_SET_CLIENT	COLLATION_CONNECTION	DATABASE_COLLATION
-def	#mysql50#a@b	tr1	INSERT	def	#mysql50#a@b	#mysql50#c@d	0	NULL	SET NEW.a = 10 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
-def	#mysql50#a@b	tr2	INSERT	def	#mysql50#a@b	t1	0	NULL	SET NEW.a = 100 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+def	#mysql50#a@b	tr1	INSERT	def	#mysql50#a@b	#mysql50#c@d	1	NULL	SET NEW.a = 10 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
+def	#mysql50#a@b	tr2	INSERT	def	#mysql50#a@b	t1	1	NULL	SET NEW.a = 100 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	latin1	latin1_swedish_ci	latin1_swedish_ci
 mysqlcheck --fix-db-names --fix-table-names --all-databases
 USE `a@b`;
 SELECT * FROM INFORMATION_SCHEMA.TRIGGERS
 WHERE TRIGGER_SCHEMA="a@b" ORDER BY trigger_name;
 TRIGGER_CATALOG	TRIGGER_SCHEMA	TRIGGER_NAME	EVENT_MANIPULATION	EVENT_OBJECT_CATALOG	EVENT_OBJECT_SCHEMA	EVENT_OBJECT_TABLE	ACTION_ORDER	ACTION_CONDITION	ACTION_STATEMENT	ACTION_ORIENTATION	ACTION_TIMING	ACTION_REFERENCE_OLD_TABLE	ACTION_REFERENCE_NEW_TABLE	ACTION_REFERENCE_OLD_ROW	ACTION_REFERENCE_NEW_ROW	CREATED	SQL_MODE	DEFINER	CHARACTER_SET_CLIENT	COLLATION_CONNECTION	DATABASE_COLLATION
-def	a@b	tr1	INSERT	def	a@b	c@d	0	NULL	SET NEW.a = 10 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	utf8	utf8_general_ci	latin1_swedish_ci
-def	a@b	tr2	INSERT	def	a@b	t1	0	NULL	SET NEW.a = 100 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	utf8	utf8_general_ci	latin1_swedish_ci
+def	a@b	tr1	INSERT	def	a@b	c@d	1	NULL	SET NEW.a = 10 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	utf8	utf8_general_ci	latin1_swedish_ci
+def	a@b	tr2	INSERT	def	a@b	t1	1	NULL	SET NEW.a = 100 * NEW.a	ROW	BEFORE	NULL	NULL	OLD	NEW	NULL		root@localhost	utf8	utf8_general_ci	latin1_swedish_ci
 INSERT INTO `c@d` VALUES (2), (1);
 SELECT * FROM `c@d`;
 a