Bug#45288: pb2 returns a lot of compilation warnings

Fix assorted compiler warnings.

include/my_pthread.h:
  Like for pthread_cond_timedwait, the abstime is constant.
mysys/my_gethwaddr.c:
  Instead of using a manual copy that introduce warnings due to
  type mismatch, copy the buffer using memcpy and use memcmp to
  check whether all bytes of the buffer are zeroed.
mysys/thr_mutex.c:
  Like for pthread_cond_timedwait, the abstime is constant.
unittest/mytap/tap.h:
  Introduce a ok() variant that does not take a format argument.
  Since ok() is tagged with a printf attribute, GCC complains if
  the fmt argument is NULL.

unittest/examples/skip-t.c

@@ -18,11 +18,11 @@
 
 int main() {
   plan(4);
-  ok(1, NULL);
-  ok(1, NULL);
+  ok1(1);
+  ok1(1);
   SKIP_BLOCK_IF(1, 2, "Example of skipping a few test points in a test") {
-    ok(1, NULL);
-    ok(1, NULL);
+    ok1(1);
+    ok1(1);
   }
   return exit_status();
 }

unittest/examples/skip_all-t.c

@@ -31,9 +31,9 @@ int main() {
   if (!has_feature())
     skip_all("Example of skipping an entire test");
   plan(4);
-  ok(1, NULL);
-  ok(1, NULL);
-  ok(1, NULL);
-  ok(1, NULL);
+  ok1(1);
+  ok1(1);
+  ok1(1);
+  ok1(1);
   return exit_status();
 }

unittest/examples/todo-t.c

@@ -21,15 +21,15 @@
 int main()
 {
   plan(4);
-  ok(1, NULL);
-  ok(1, NULL);
+  ok1(1);
+  ok1(1);
   /*
     Tests in the todo region is expected to fail. If they don't,
     something is strange.
   */
   todo_start("Need to fix these");
-  ok(0, NULL);
-  ok(0, NULL);
+  ok1(0);
+  ok1(0);
   todo_end();
   return exit_status();
 }