Replace %ld with %jd and cast to intmax_t

Replace %ld with %jd and cast to intmax_t

On x32, GCC 5.1 complains:

tst-fmemopen2.c: In function ‘do_test_without_buffer’:
tst-fmemopen2.c:124:15: error: format ‘%ld’ expects argument of type ‘long int’, but argument 2 has type ‘off_t {aka long long int}’ [-Werror=format=]
       printf ("FAIL: first ftello returned %ld, expected %zu\n", o, nstr);
               ^
tst-fmemopen2.c:135:15: error: format ‘%ld’ expects argument of type ‘long int’, but argument 2 has type ‘off_t {aka long long int}’ [-Werror=format=]
       printf ("FAIL: second ftello returned %ld, expected %zu\n", o, nbuf);
               ^
tst-fmemopen2.c:148:15: error: format ‘%ld’ expects argument of type ‘long int’, but argument 2 has type ‘off_t {aka long long int}’ [-Werror=format=]
       printf ("FAIL: third ftello returned %ld, expected %zu\n", o, nstr2);
               ^
tst-fmemopen2.c: In function ‘do_test_length_zero’:
tst-fmemopen2.c:183:15: error: format ‘%ld’ expects argument of type ‘long int’, but argument 2 has type ‘off_t {aka long long int}’ [-Werror=format=]
       printf ("FAIL: first ftello returned %ld, expected 0\n", o);
               ^

This patch silences GCC.

	* stdio-common/tst-fmemopen2.c (do_test_without_buffer): Replace
	%ld with %jd and cast to intmax_t.
	(do_test_length_zero): Likewise.