2. Correct some logical bugs within the tests, which were caused by
   automatic resolve of BitKeeper


mysql-test/include/mix1.inc:
  - Remove hardcoded assignment of storage engine, because this violates the logics of
    refactored tests
  - Remove trailing spaces
  - Move the FOREIGN KEY creation(probably not really needed for the testcase) out of 
    the CREATE TABLE statement + let the FK creation depend on the storage engine capabilities
mysql-test/r/index_merge_innodb.result:
  Updated result
mysql-test/r/index_merge_myisam.result:
  Updated result
mysql-test/r/innodb_mysql.result:
  Updated result
mysql-test/t/disabled.def:
  Reenable the fixed tests
mysql-test/t/index_merge_innodb.test:
  Important comment describing how to modify the tests when some issues
  (most probably no bugs) are fixed.
mysql-test/t/innodb_mysql.test:
  Introduction of a variable for switching FOREIGN KEY on/off