Since Autoconf places some important feature flags only into the
configuration header, it is necessary to include it globally to
guarantee a consistent build.
This requires sr_hw_cleanup_all() and sanity_check_all_drivers()
to also take a context.
The (runtime) generation of the driver list now happens in sr_init()
and sr_driver_list() always returns that pre-generated list. This fixes
a segfault when (correctly) invoking multiple sr_init() and sr_exit()
calls with different contexts (caught by the unit tests).
This fixes bug #565.
Daniel Elstner
Uwe Hermann