ENG-6478: Allow LIMIT PARTITION ROWS to be set, changed, and dropped

using ALTER TABLE
Typo (here and elsewhere) in structured comment -- "extension" not spelled canonically (Extention, extention, other?).
I've got a fussy little script that extracts the voltisms for ease of diffing with upstream HSQL, past and future, and it will gag on these. 
Under most circumstances, a miss like these is easily picked up by a visual scan of the script output (diff with past HSQL), and so is easy enough to correct later, but nipping it in the bud now that I'm seeing it will save a little churning later