Re: minor doc work

Neil Conway wrote:
> If <command>SET</> is allowed, it overrides all other sources of
> ! values for the parameter. Superusers are allowed to
> ! <command>SET</> more values than ordinary users. Some parameters
> ! cannot be <command>SET</command> even by superusers: for example,

Please don't use marked up command names as verbs. Next week you'll be
<command>UPDATE</command>ing or something. Here, there is no chance for
confusion, so just write "cannot be set" or "cannot be changed with
<command>SET</command>". In fact, the latter is even clearer.

> ! if they control behavior that cannot reasonably be changed without
> ! restarting <productname>PostgreSQL</productname>.