syslog: fix argument printing

syslog: fix argument printing

* syslog.c (SYS_FUNC(syslog)): Store conversion to int of tcp->u_arg[2]
in len; print address using printaddr64 (as syslog doesn't use compat
for x32), and third argument as int (as it has this type in the syscall
handler).
* tests/syslog.c: Add checks.