Fix packet filename in "Gruned message" log entry on Win32

e.g. "Grunged message (type 2) from 4:80/1 at offset 58 in packet: (null)"

off_t is 64-bit, but long in 32-bit (on Win32), so needs a typecast here in
lprintf() call (otherwise, the upper 4 bytes of the offset are interpreted
as the string address for the corresponding '%s' argument, the filename).
14 jobs for master in 12 minutes and 58 seconds (queued for 13 seconds)
Status Job ID Name Coverage
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passed #34507
FreeBSD
jsdoor-freebsd

00:04:06

passed #34508
Linux
jsdoor-linux

00:08:16

passed #34510
FreeBSD
jsdoor-windows

00:01:57

passed #34502
FreeBSD
sbbs-freebsd

00:05:47

passed #34497
Linux
sbbs-linux

00:12:54

passed #34500
Windows
sbbs-windows

00:05:12

passed #34509
FreeBSD
sexpots-freebsd

00:00:15

passed #34498
Linux
sexpots-linux

00:00:24

passed #34501
Windows
sexpots-windows

00:00:35

passed #34505
FreeBSD
syncdraw-freebsd

00:00:31

passed #34506
Linux
syncdraw-linux

00:01:02

passed #34503
FreeBSD
syncterm-freebsd

00:01:09

passed #34499
Linux
syncterm-linux

00:02:56

passed #34504
FreeBSD
syncterm-windows

00:01:55