Fix time_t handling in parsing F5 session timeout

Fix time_t handling in parsing F5 session timeout

We can't assume that time_t is 'long'. When building for win64 we get:
../f5.c: In function 'f5_configure':
../f5.c:690:63: warning: format '%ld' expects argument of type 'long int *', but argument 6 has type 'time_t *' {aka 'long long int *'} [-Wformat=]
  690 |                         if (sscanf(cookie->value, "%dz%dz%dz%ldz%ld%c", &junk, &junk, &junk, &start, &dur, &c) >= 5
      |                                                             ~~^                              ~~~~~~
      |                                                               |                              |
      |                                                               long int *                     time_t * {aka long long int *}
      |                                                             %lld
../f5.c:690:67: warning: format '%ld' expects argument of type 'long int *', but argument 7 has type 'time_t *' {aka 'long long int *'} [-Wformat=]
  690 |                         if (sscanf(cookie->value, "%dz%dz%dz%ldz%ld%c", &junk, &junk, &junk, &start, &dur, &c) >= 5
      |                                                                 ~~^                                  ~~~~
      |                                                                   |                                  |
      |                                                                   long int *                         time_t * {aka long long int *}
      |                                                                 %lld

Make it explicitly 'unsigned long long' instead.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>