tests: Silence warnings in template

- no previous prototype for ‘test_assert’
- no previous prototype for ‘test_count’
- unused parameter ‘b’ in test_count
- function declaration isn’t a prototype for main

tests/template.fmt

@@ -7,11 +7,11 @@
 
 
 // test stuff
-void test_log(const char *s, uintmax_t v) {{
+static void test_log(const char *s, uintmax_t v) {{
  printf("%s: %jd\n", s, v);
 }}
 
-void test_assert(const char *file, unsigned line,
+static void test_assert(const char *file, unsigned line,
  const char *s, uintmax_t v, uintmax_t e) {{
  static const char *last[6] = {{0, 0}};
  if (v != e || !(last[0] == s || last[1] == s ||
@@ -37,7 +37,8 @@ void test_assert(const char *file, unsigned line,
 
 
 // utility functions for traversals
-int test_count(void *p, lfs_block_t b) {{
+static int __attribute__((used)) test_count(void *p,
+ lfs_block_t b __attribute__((unused))) {{
  unsigned *u = (unsigned*)p;
  *u += 1;
  return 0;
@@ -96,7 +97,7 @@ const struct lfs_config cfg = {{
 
 
 // Entry point
-int main() {{
+int main(void) {{
  lfs_emubd_create(&cfg, "blocks");
 
 {tests}