Re: Fix typos and inconsistencies for HEAD (take 7)

Fixing both places sounds adapted to me.  An alternative we could use
here is just to say something like that:
The effective resolution is only 1/HZ, which can be configured with
kernel parameter (see man 7 time), and is 4 milliseconds by
default.

Whatever we say here is going to be a lie on some platforms.

Probably best just to say that the sleep resolution is platform-dependent
and leave it at that.

I think, we can say "on many systems"/ "on most Unixen", and it would not be a lie.
In my opinion, while a generic reference to platform-dependency is OK for developer' documentation, it makes the following passage in config.sgml vague (we don't give user a hint, what "the effective resolution" can be - several seconds/milliseconds/nanoseconds?):
The default value is 200 milliseconds (<literal>200ms</literal>). Note that on many systems, the
effective resolution of sleep delays is 10 milliseconds; setting
<varname>bgwriter_delay</varname> to a value that is not a multiple of 10
might have the same results as setting it to the next higher multiple of 10.
->
The default value is 200 milliseconds (<literal>200ms</literal>). Note that the
effective resolution of sleep delays is paltform-dependent. setting
<varname>bgwriter_delay</varname> to a value that is not a multiple of the effective resolution,
might have the same results as setting it to the next higher multiple.

Best regards,
Alexander