First steps at getting recovery back off the ground:

First steps at getting recovery back off the ground:
* make the callback data parameter to brw functions be strongly typed as
  cb_io_data.  LOV and other non-OSC users of these facilities should
  "inherit" from this struct, see lov_callback_data for an example.
* replace l_wait_event_killable and some wait_event calls with
  l_wait_event, an all-singing, all-dancing timeout- and interrupt-handling
  event waiting macro.  More such replacement to come.
* interrupt and timeout handling of bulk data will probably crash at present,
  but it didn't really work before either -- I'll fix it up ASAP.