Implement DEFCFUN-HELPER idea.
Implement DEFCFUN-HELPER idea.

 - cffi-sys implementations can now define a defcfun-helper
   function that returns two forms, a prelude and a caller.
   (todo: explain this better in the code/doc)
 - changed foreign-funcall-1 to translate-objects
   (also todo: document translate-objects)

stassats/cffi,attila-lendvai/cffi,wesen/cffi,3b/cffi,cffi/cffi,akovalenko/cffi,kingcheez/cffi-cheez,dkochmanski/cffi,dochang/cffi,dochang/cffi,kingcheez/cffi-cheez,3b/cffi,3b/cffi,attila-lendvai/cffi,dkochmanski/cffi,cffi/cffi,cffi/cffi,stassats/cffi,wesen/cffi,marsijanin/cffi,wesen/cffi,akovalenko/cffi,dochang/cffi,stassats/cffi,mcna/cffi,mcna/cffi,dkochmanski/cffi,marsijanin/cffi,kingcheez/cffi-cheez,marsijanin/cffi,akovalenko/cffi