examples/ld_iscsi.c: format string int on 32bit

This patch uses appropriate format string specifiers for uint64_t
types taken from inttypes.h, instead of using %lu, because %lu is
wrong at least on 32bit architecture.

Also, cast size_t expressions to unsigned long, again, because on at least
32bit architectures, size_t is int, not long.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>