Update the intent on SI-style separators.

[ghost]

Clean up of #5372

[laanwj]

Shouldn't this be SI-style instead of SI-stule?

[ghost]

Fixed both typos, "SI-stule" and "indendent".

[sipa]

I'm confused. I thought the small-spaces-separators thing got reverted? (no opinion either way here; just asking what this is about...)

[ghost]

Apparently thin spaces are still alive and kicking, but only to the left of the decimal marker, and regardless of the number of digits involved in the quotient (of course greater than 3 that is, but not 4). So this commit is no more but the code comment catching up with the code. The code rationale itself is covered by Wladimir in #5372.

[laanwj]

Only separators to the right of the decimal point were reverted. IMO as non-physicist it was too hard to get used to digit grouping after the point.