Fixes bugs:
- Bug #20877: InnoDB data dictionary memory footprint is too big
- Bug #24741: existing cascade clauses disappear when adding foreign keys


mysql-test/r/innodb.result:
  Applied innodb-5.1-ss1186
  
  Revision r1186:
  dict_load_foreign(): Use a local variable instead of the 10-bit field
  foreign->n_fields in order to preserve ON UPDATE CASCADE and
  ON DELETE CASCADE flags.  For some reason, gcc does not warn about
  shifting a 10-bit field to right by 24 bits.  (Bug #24741)
  
  This bug was introduced while reducing the memory footprint of the
  InnoDB data dictionary (Bug #20877).
  
  innodb.test, innodb.result: Add a test case.
mysql-test/t/innodb.test:
  Applied innodb-5.1-ss1186
  
  Revision r1186:
  dict_load_foreign(): Use a local variable instead of the 10-bit field
  foreign->n_fields in order to preserve ON UPDATE CASCADE and
  ON DELETE CASCADE flags.  For some reason, gcc does not warn about
  shifting a 10-bit field to right by 24 bits.  (Bug #24741)
  
  This bug was introduced while reducing the memory footprint of the
  InnoDB data dictionary (Bug #20877).
  
  innodb.test, innodb.result: Add a test case.
storage/innobase/buf/buf0flu.c:
  Applied innodb-5.1-ss1186
  
  Revision r1168:
  buf_flush_batch(): Remove the test page_count != ULINT_UNDEFINED.
  The variable is initialized to zero, and after that it is only added to.
  Maybe the one who introduced the variable srv_buf_pool_flushed overlooked
  that there is a separate return statement for returning ULINT_UNDEFINED?
storage/innobase/dict/dict0load.c:
  Applied innodb-5.1-ss1186
  
  Revision r1186:
  dict_load_foreign(): Use a local variable instead of the 10-bit field
  foreign->n_fields in order to preserve ON UPDATE CASCADE and
  ON DELETE CASCADE flags.  For some reason, gcc does not warn about
  shifting a 10-bit field to right by 24 bits.  (Bug #24741)
  
  This bug was introduced while reducing the memory footprint of the
  InnoDB data dictionary (Bug #20877).
  
  innodb.test, innodb.result: Add a test case.
storage/innobase/include/ut0ut.h:
  Applied innodb-5.1-ss1186
  
  Revision r1165:
  ut_2_power_up(): Add __attribute__((const)), because otherwise this function
  is repeatedly called in buf_flush_free_margin() due to the definitions
  of BUF_READ_AHEAD_AREA and other macros starting with BUF_READ_AHEAD_.
storage/innobase/que/que0que.c:
  Applied innodb-5.1-ss1186
  
  Revision r1158:
  Modify que_fork_start_command() to do only one pass over the thread list
  instead of three.