* tests which use MERGE or INSERT DELAYED should run only

with engines which support that
* temporarily adding option --global-subst to mysqltest so that
the full testsuite can be run using Maria tables without failing
on trivial differences (like diff in the engine clause of
SHOW CREATE TABLE)
* using recognizable tags for todos of the Maria team


client/mysqltest.c:
  temporarily adding option --global-subst: its argument is X,Y.
  It replaces all occurrences of X by Y into mysqltest's result
  before the comparison with the expected result is done.
  This serves for when a test is run with --default-storage-engine=X
  where X is not MyISAM: tests using SHOW CREATE TABLE will always fail
  because SHOW CREATE TABLE prints X instead of MyISAM. With
  --global-subst=X,MyISAM , such trivial differences are eliminated and
  test may be reported as passing.
  For example, --global-subst=MARIA,MyISAM
  This is not good enough for merging into main trees! just for running
  many tests and finding bugs now!
mysql-test/mysql-test-run.pl:
  new option --mysqltest to pass options to mysqltest (like we have
  --mysqld). Used for example like this:
  ./mtr --mysqltest=--global-subst=MARIA,MyISAM
mysql-test/r/merge.result:
  update
mysql-test/t/delayed.test:
  run test only with engines which support INSERT DELAYED
mysql-test/t/merge.test:
  run test only with MyISAM tables, as they are required by MERGE
sql/sql_delete.cc:
  recognizable tag
sql/table.cc:
  recognizable tag
storage/maria/ha_maria.cc:
  recognizable tag
storage/maria/ma_check.c:
  recognizable tag
storage/maria/ma_create.c:
  recognizable tag

mysql-test/r/merge.result

@@ -1,3 +1,5 @@
+set global storage_engine=myisam;
+set session storage_engine=myisam;
 drop table if exists t1,t2,t3,t4,t5,t6;
 drop database if exists mysqltest;
 create table t1 (a int not null primary key auto_increment, message char(20));