Fix interposition of clock_gettime64

timespec.tv_nsec is 32-bit, even though timeval.tv_usec is
64-bit (weirdly).  This doesn't matter very much in practice because
 * on little endian architectures (which is all our 32-bit release
   arches) writing to a too big integer ends up writing the
   desired value in the desired location, and
 * it doesn't affect the overall struct size on any of our actual
   architectures (which align the uint64_t to 8 so must make the
   whole struct 16 not 12), so the write overflow is harmless.

> #include <time.h>
> #include <sys/time.h>
> #include <stdio.h>
> struct timeval tv;
> struct timespec ts;
> int main(void) {
>    printf("time_t %lld\n", (unsigned long long) sizeof(time_t));
>    printf("timeval %lld %lld %lld\n",
>           (unsigned long long) sizeof(tv),
>           (unsigned long long) sizeof(tv.tv_sec),
>           (unsigned long long) sizeof(tv.tv_usec)
>           );
>    printf("timespec %lld %lld %lld\n",
>           (unsigned long long) sizeof(ts),
>           (unsigned long long) sizeof(ts.tv_sec),
>           (unsigned long long) sizeof(ts.tv_nsec)
>           );
> }
> (sid_armhf-dchroot)iwj@amdahl:~/Faketime/test$ gcc t.c
> (sid_armhf-dchroot)iwj@amdahl:~/Faketime/test$ ./a.out
> time_t 8
> timeval 16 8 8
> timespec 16 8 4
> (sid_armhf-dchroot)iwj@amdahl:~/Faketime/test$

src/libfaketime.c

@@ -168,7 +168,7 @@ struct utimbuf {
 struct __timespec64
 {
   uint64_t tv_sec;         /* Seconds */
-  uint64_t tv_nsec;        /* Nanoseconds */
+  uint32_t tv_nsec;        /* this is 32-bit, apparently! */
 };
 
 /*