Allow a parameter to smb_thread_once's initialization function

Allow a parameter to smb_thread_once's initialization function

- This should make life easier for ourselves. We're no longer constrained to
  the semantics of pthread_once, so let's allow passing a parameter to the
  initialization function. Some of Samba's init functions return a
  value. Although I haven't searched, I suspect that some of the init
  functions require in input parameters. The parameter added here can be used
  for input, output, or both, as necessary... or ignored, as is now done in
  talloc_stackframe_init().

Derrell