Added --strace support to mysql-test-run

mysql-test/mysql-test-run.pl:
  Added support for --strace (usefull for example to check how much memory mysqld was using)
mysql-test/suite/funcs_1/t/is_engines_innodb.test:
  Fixed test case to also work with xtradb
mysql-test/suite/innodb_plugin/t/innodb.test:
  Don't run if we don't have the used character sets.
mysql-test/suite/innodb_plugin/t/innodb_mysql.test:
  Don't run if we don't have the used character sets.
sql/sql_show.cc:
  Extended comment to 160 characters to get full comment from xtradb
storage/xtradb/handler/ha_innodb.cc:
  Fixed valgrind warning.