Use off_t in for constants used in iprop log seeks

On 32-bit architectures with _FILE_OFFSET_BITS=64,
 sizeof(off_t) > sizeof(size_t) .

LOG_HEADER_SZ was #define'd as an expression of type size_t, so in order
to get the sign extension right we need -(off_t)LOG_HEADER_SZ instead of
(off_t)(-LOG_HEADER_SZ).  However, we can just define the *_SZ macros to
cast to off_t, then we don't need to worry about negation.

Fixes Debian bug #822749, PR 175.

Signed-off-by (and updated by): Nicolas Williams <nico@twosigma.com>

lib/kadm5/log.c

@@ -174,11 +174,11 @@ RCSID("$Id$");
  * will deadlock with ipropd-slave -- don't do that.
  */
 
-#define LOG_HEADER_SZ   (sizeof(uint32_t) * 4)
-#define LOG_TRAILER_SZ  (sizeof(uint32_t) * 2)
-#define LOG_WRAPPER_SZ  (LOG_HEADER_SZ + LOG_TRAILER_SZ)
-#define LOG_UBER_LEN    (sizeof(uint64_t) + sizeof(uint32_t) * 2)
-#define LOG_UBER_SZ     (LOG_WRAPPER_SZ + LOG_UBER_LEN)
+#define LOG_HEADER_SZ   ((off_t)(sizeof(uint32_t) * 4))
+#define LOG_TRAILER_SZ  ((off_t)(sizeof(uint32_t) * 2))
+#define LOG_WRAPPER_SZ  ((off_t)(LOG_HEADER_SZ + LOG_TRAILER_SZ))
+#define LOG_UBER_LEN    ((off_t)(sizeof(uint64_t) + sizeof(uint32_t) * 2))
+#define LOG_UBER_SZ     ((off_t)(LOG_WRAPPER_SZ + LOG_UBER_LEN))
 
 #define LOG_NOPEEK 0
 #define LOG_DOPEEK 1