Minor implementation changes

[Sven Hartrumpf <Sven.Hartrumpf@xxxxxxxxxxxxxxxx>]

Hi all.
The current implementation looks fine.
There are 3 places where one could save some bytes and/or some
milliseconds.

1. (display #\newline buffer)->(newline buffer)

2. (display #\~ buffer)->(write-char #\~ buffer)

3. (display (car format-list) buffer)->(write-char (car format-list) buffer)

Ciao
Sven