Cast to (void *) rather than (int *) when passing int64's to PQfn().

This is a possibly-vain effort to silence a Coverity warning about
bogus endianness dependency.  The code's fine, because it takes care
of endianness issues for itself, but Coverity sees an int64 being
passed to an int* argument and not unreasonably suspects something's
wrong.  I'm not sure if putting the void* cast in the way will shut it
up; but it can't hurt and seems better from a documentation standpoint
anyway, since the pointer is not used as an int* in this code path.

Just for a bit of additional safety, verify that the result length
is 8 bytes as expected.

Back-patch to 9.3 where the code in question was added.

src/interfaces/libpq/fe-lobj.c

@@ -290,7 +290,7 @@ lo_read(PGconn *conn, int fd, char *buf, size_t len)
 	argv[1].u.integer = (int) len;
 
 	res = PQfn(conn, conn->lobjfuncs->fn_lo_read,
-			   (int *) buf, &result_len, 0, argv, 2);
+			   (void *) buf, &result_len, 0, argv, 2);
 	if (PQresultStatus(res) == PGRES_COMMAND_OK)
 	{
 		PQclear(res);
@@ -441,8 +441,8 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	argv[2].u.integer = whence;
 
 	res = PQfn(conn, conn->lobjfuncs->fn_lo_lseek64,
-			   (int *) &retval, &result_len, 0, argv, 3);
-	if (PQresultStatus(res) == PGRES_COMMAND_OK)
+			   (void *) &retval, &result_len, 0, argv, 3);
+	if (PQresultStatus(res) == PGRES_COMMAND_OK && result_len == 8)
 	{
 		PQclear(res);
 		return lo_ntoh64(retval);
@@ -607,8 +607,8 @@ lo_tell64(PGconn *conn, int fd)
 	argv[0].u.integer = fd;
 
 	res = PQfn(conn, conn->lobjfuncs->fn_lo_tell64,
-			   (int *) &retval, &result_len, 0, argv, 1);
-	if (PQresultStatus(res) == PGRES_COMMAND_OK)
+			   (void *) &retval, &result_len, 0, argv, 1);
+	if (PQresultStatus(res) == PGRES_COMMAND_OK && result_len == 8)
 	{
 		PQclear(res);
 		return lo_ntoh64(retval);