Out of bound access for get_arpadate function

[Syed-Shahrukh-OSSRevival]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=724279

I just ran the static analysis tool "cppcheck" over the source
code of ssmtp-2.64

It said many things, including

[arpadate.c:70]: (error) Buffer is accessed out of bounds.
[arpadate.c:72]: (error) Buffer is accessed out of bounds.

Source code is

 
  if (offset>= 0)
    sprintf (timezone, "+%02d%02d", offset / 60, offset % 60);
  else
    sprintf (timezone, "-%02d%02d", -offset / 60, -offset % 60);
 

so that's six bytes written into timezone. But

static char timezone[3];

Suggest increase size of timezone