The '%z' format character isn't functional. Try the following:

#define _XOPEN_SOURCE
#define _BSD_SOURCE
#include <time.h>
#include <stdio.h>

int main(void)
{
	struct tm tm;

	strptime("1113472456 +1000", "%s %z", &tm);

	if (tm.tm_gmtoff == 36000) {
		printf("OK");
		return 0;
	} else {
		printf("Error: tm_gmtoff is %ld\n", tm.tm_gmtoff);
		return 1;
	}
}

The man page states that "In most cases the corresponding fields are parsed, but
no field in tm is changed.". I assume that in the case of at least %F and %z,
the field in tm _should_ be changed.