Make eligible functions static

The codebase is already very disciplined in making any function which
can be `static`, but there are a few that appear to have slipped through
the cracks.

test/unit/bit_util.c

@@ -48,7 +48,7 @@ TEST_BEGIN(test_pow2_ceil_zu) {
 }
 TEST_END
 
-void
+static void
 expect_lg_ceil_range(size_t input, unsigned answer) {
 	if (input == 1) {
 		expect_u_eq(0, answer, "Got %u as lg_ceil of 1", answer);
@@ -60,7 +60,7 @@ expect_lg_ceil_range(size_t input, unsigned answer) {
 	    "Got %u as lg_ceil of %zu", answer, input);
 }
 
-void
+static void
 expect_lg_floor_range(size_t input, unsigned answer) {
 	if (input == 1) {
 		expect_u_eq(0, answer, "Got %u as lg_floor of 1", answer);

test/unit/double_free.c

@@ -9,19 +9,20 @@ void fake_abort(const char *message) {
 	fake_abort_called = true;
 }
 
-void
+static void
 test_double_free_pre(void) {
 	safety_check_set_abort(&fake_abort);
 	fake_abort_called = false;
 }
 
-void
+static void
 test_double_free_post() {
 	expect_b_eq(fake_abort_called, true, "Double-free check didn't fire.");
 	safety_check_set_abort(NULL);
 }
 
-bool tcache_enabled() {
+static bool
+tcache_enabled() {
 	bool enabled;
 	size_t sz = sizeof(enabled);
 	assert_d_eq(

test/unit/nstime.c

@@ -201,7 +201,7 @@ TEST_BEGIN(test_nstime_divide) {
 }
 TEST_END
 
-void
+static void
 test_nstime_since_once(nstime_t *t) {
 	nstime_t old_t;
 	nstime_copy(&old_t, t);

test/unit/pa.c

@@ -48,7 +48,8 @@ struct test_data_s {
 	extent_hooks_t hooks;
 };
 
-test_data_t *init_test_data(ssize_t dirty_decay_ms, ssize_t muzzy_decay_ms) {
+static test_data_t *
+init_test_data(ssize_t dirty_decay_ms, ssize_t muzzy_decay_ms) {
 	test_data_t *test_data = calloc(1, sizeof(test_data_t));
 	assert_ptr_not_null(test_data, "");
 	init_test_extent_hooks(&test_data->hooks);

test/unit/size_check.c

@@ -14,7 +14,7 @@ void fake_abort(const char *message) {
 #define LARGE_SIZE1 SC_LARGE_MINCLASS
 #define LARGE_SIZE2 (LARGE_SIZE1 * 2)
 
-void *
+static void *
 test_invalid_size_pre(size_t sz) {
 	safety_check_set_abort(&fake_abort);
 
@@ -25,7 +25,7 @@ test_invalid_size_pre(size_t sz) {
 	return ptr;
 }
 
-void
+static void
 test_invalid_size_post(void) {
 	expect_true(fake_abort_called, "Safety check didn't fire");
 	safety_check_set_abort(NULL);