fix compilation with gcc 10

Here is the compilation error:

686-w64-mingw32-gcc -DHAVE_CONFIG_H -I. -I./src   -I/builds/robUx4/vlc/contrib/i686-w64-mingw32/include  -Wall -Werror  -I/builds/robUx4/vlc/contrib/i686-w64-mingw32/include -g -O0 -c -o src/b25-td.o `test -f 'src/td.c' || echo './'`src/td.c
src/td.c: In function 'test_arib_std_b25':
src/td.c:376:50: error: format '%d' expects argument of type 'int', but argument 3 has type 'int64_t' {aka 'long long int'} [-Werror=format=]
  376 |    fprintf(stderr, "  undecrypted TS packet: %I64d\n", pgrm.undecrypted_packet_count);
      |                                              ~~~~^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                                  |         |
      |                                                  int       int64_t {aka long long int}
      |                                              %I64lld
src/td.c:377:50: error: format '%d' expects argument of type 'int', but argument 3 has type 'int64_t' {aka 'long long int'} [-Werror=format=]
  377 |    fprintf(stderr, "  total TS packet:       %I64d\n", pgrm.total_packet_count);
      |                                              ~~~~^     ~~~~~~~~~~~~~~~~~~~~~~~
      |                                                  |         |
      |                                                  int       int64_t {aka long long int}
      |                                              %I64lld
cc1: all warnings being treated as errors
Makefile:630: recipe for target 'src/b25-td.o' failed