Add --skip-innodb-adaptive-hash-index option, which is a way to
work around the bug (by disabling the adaptive hash feature entirely).

This may be useful even once the bug is fixed, for benchmarking purposes.
There are some workloads for which the adaptive hash index is not effective.


sql/ha_innodb.cc:
  Add --skip-innodb-adaptive-hash-index option.
sql/ha_innodb.h:
  Add --skip-innodb-adaptive-hash-index option.
sql/mysqld.cc:
  Add --skip-innodb-adaptive-hash-index option.
sql/set_var.cc:
  Add --skip-innodb-adaptive-hash-index option.