ChangeTags: Show checkbox on Special:Log when user lacks RevDel rights
The actual production of checkboxes in LogEventsList didn't get updated
to show checkboxes when the user can edit change tags but cannot use
RevDel on log entries.
This also renames LogEventsList::USE_REVDEL_CHECKBOXES to
LogEventsList::USE_CHECKBOXES to be accurate with the change here; no
extensions in Gerrit use this constant, so we should be safe.