From: Rusty Russell <rusty@rustcorp.com.au>

Brian Gerst's patch which moved __this_module out from module.h into the
module post-processing had a side effect.  genksyms didn't see the
undefined symbols for modules without a module_init (or module_exit), and
hence didn't generate a version for them, causing the kernel to be tainted.

The simple solution is to always include the versions for these functions. 
Also includes two cleanups:

1) alloc_symbol is easier to use if it populates ->next for us.

2) add_exported_symbol should set owner to module, not head of module
   list (we don't use this field in entries in that list, fortunately).