static cache for thread_load

Can we instead port d7 drupal_static with pmsg namespace function name? does it fit the use case ?

Tested and this works as expected.

Little code nitpick.

Please reivew.

reroll of the static_nesting patch since I assume that is the approach that is preferred over the early return?

There is a slight change in code too - in the last there was

+      if (empty($thread['messages'])) {
+        $threads[$account->uid][$thread_id] = FALSE;
+      } else {
+        // general data, assume subject is the same for all messages of that thread.
+        $thread['user'] = $account;
+        $message = current($thread['messages']);
+        $thread['subject'] = $message['subject'];
+
+        $threads[$account->uid][$thread_id] = $thread;
+      }

I changed that to

+      if (empty($thread['messages'])) {
+        $thread = FALSE;
+      } else {
+        // general data, assume subject is the same for all messages of that thread.
+        $thread['user'] = $account;
+        $message = current($thread['messages']);
+        $thread['subject'] = $message['subject'];
+      }
+      $threads[$account->uid][$thread_id] = $thread;

This is not really a big patch - the majority of line changes are in indentation due to being inside another if statement - compare it to early return patch in the previous comment to see how small the functional changes really are.