Fix change OCS_off_t to a signed type
The C library type is signed, and this makes the
result check work as intended.
/* types normally defined in sys/types.h */
/* ----------------------------------------- */
typedef ptrdiff_t OCS_ssize_t;
-typedef size_t OCS_off_t;
+typedef long OCS_off_t;
typedef unsigned int OCS_mode_t;
typedef long OCS_time_t;
typedef int OCS_pid_t;
