postgresql.auto.conf comments

Hi,

I haven't seen this mentioned anywhere (although it may have as I haven't
read through the entire history of it), but would others find it useful to
have ALTER SYSTEM support comments?

e.g.

ALTER SYSTEM SET autovacuum_vacuum_scale_factor = 0.01
WITH [ INLINE | HEADLINE ] COMMENT $$As most of the tables on the system
are so big, we're setting this parameter lower than the default to keep
bloat under more control.$$;

I just made up inline and headline to suggest that we could allow either:

autovacuum_vacuum_scale_factor = 0.01 # As most of the tables...

and

# As most of the tables on the system are so big, we're setting this
parameter
# lower than the default to keep bloat under more control.
autovacuum_vacuum_scale_factor = 0.01

The rationale being that it's often the case one wants to document the
reason for a parameter being configured so, but there's no way of doing
this for settings in postgresql.auto.conf as they'll be wiped out if added
manually.

Thom