foreach: fixed maybe uninitialized warning in test (-O2)

/home/rusty/devel/cvs/ccan/ccan/tap/tap.h:57:59: warning: ‘max_iters’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    _gen_result(1, __func__, __FILE__, __LINE__, "%s", #e) : \
                                                           ^
/home/rusty/devel/cvs/ccan/ccan/foreach/test/run-nested.c:47:17: note: ‘max_iters’ was declared here
  int i, j, sum, max_iters;
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/foreach/test/run-nested.c

@@ -44,7 +44,7 @@ static int count_iters(void)
 
 int main(void)
 {
-	int i, j, sum, max_iters;
+	int i, j, sum, max_iters = 0 /* keep gcc happy */;
 	const char *istr, *jstr;
 
 	plan_tests(13);