WL#3136: Maria - optional improvements not needed in first version

Master Worklog entry for each RawIdeaBin idea which at least one dev
thinks (and no dev strongly opposes):
- is not a lot of work
- could be good to have in some version of Maria but is not required in the first
version; i.e. probably not needed to be an InnoDB replacement but could be
needed to outperform InnoDB.
It's not impossible that mgmt decides to implement some of these ideas in the
first version, if appropriate and schedule permits.