Support building with -Werror=strict-prototypes / -Werror=old-style-definition

Unfortunately "-std=c99" is not sufficient to make gcc ignore code that
uses constructs of earlier C standards, which were abandoned in C99.

See https://lwn.net/ml/fedora-devel/Y1kvF35WozzGBpc8@redhat.com/ for
some related discussion.

Change-Id: I84fd99442d0cc400fa562fa33623c142649230e2
diff --git a/tests/use_count/use_count_test.c b/tests/use_count/use_count_test.c
index 2942c69..b784aeb 100644
--- a/tests/use_count/use_count_test.c
+++ b/tests/use_count/use_count_test.c
@@ -192,7 +192,7 @@
 	return foo;
 }
 
-void print_foos()
+void print_foos(void)
 {
 	int count = 0;
 	struct foo *foo;
@@ -204,7 +204,7 @@
 	fprintf(stderr, "%d foos\n\n", count);
 }
 
-static void test_use_count_fsm()
+static void test_use_count_fsm(void)
 {
 	struct foo *a, *b, *c;
 	log("\n%s()\n", __func__);