Filed doesn't respond to first connection after start.

The setup of the thread specific key is flawed. In essence
its setup twice (once via the init_msgs() call and once
via the pthread_once call in jcr.c). This new code fixes
that by:

- Setup thread specific data key only once.
- Use pthread_key_create_once_np when available.
  This is a non portable but cleaner implementation of
  both a pthread_once() and a pthread_key_create().
- For Windows use a workaround around pthread_once() as that
  seems to hang for unknown reason. Now we use a boolean
  protected by an mutex to make sure the setup is only done once.

Fixes #210: Filed doesn't respond to first connection after start.
Always use CoInitializeEx with multithread option.