Write the first n characters of a string on the display
void SLsmg_write_nstring (char *s, unsigned int n);
SLsmg_write_nstring writes the first n characters of
s to this virtual display. If the length of the string
s is less than n, the spaces will used until
n characters have been written. s can be NULL, in
which case n spaces will be written.
SLsmg_write_string, SLsmg_write_nchars