* 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/mysql-test-run.pl

@@ -167,6 +167,7 @@ our $opt_small_bench= 0;
 our $opt_big_test= 0;
 
 our @opt_extra_mysqld_opt;
+our @opt_extra_mysqltest_opt;
 
 our $opt_compress;
 our $opt_ssl;
@@ -558,6 +559,9 @@ sub command_line_setup () {
              # Extra options used when starting mysqld
              'mysqld=s'                 => \@opt_extra_mysqld_opt,
 
+             # Extra options used when starting mysqld
+             'mysqltest=s'                 => \@opt_extra_mysqltest_opt,
+
              # Run test on running server
              'extern'                   => \$opt_extern,
              'ndb-connectstring=s'       => \$opt_ndbconnectstring,
@@ -4794,6 +4798,11 @@ sub run_mysqltest ($) {
     mtr_add_arg($args, "--skip-ssl");
   }
 
+  foreach my $arg ( @opt_extra_mysqltest_opt )
+  {
+    mtr_add_arg($args, "%s", $arg);
+  }
+
   # ----------------------------------------------------------------------
   # If embedded server, we create server args to give mysqltest to pass on
   # ----------------------------------------------------------------------