- port Regex_list_handler from facebook/mysql-5.6/sql/handler.cc
  put it into a separate file in storage/rocksdb directory

- Adjust the build process so that the main library is build with
  Regex_list_handler (which has dependencies on the server),
  while RocksDB tools are built without it.

- Un-comment @@rdb_collation_exceptions handling in ha_rocksdb.cc
- Also adjust rocksdb_set_collation_exception_list() to free the
  old variable value and alloc the new one.