RFC: INLINE defcfun and auto FTYPE declarations [with patch]

Dear CFFI developers!

Recently we have migrated one of our largest projects from our home-grown foreign-function interface implementation to CFFI. The project is almost 1M LOC with almost 1K of foreign-functions.

Previously, we have inlined all of our foreign-function stubs. We also use FTYPEs through the code for type-safety and optimization. Having CFFI functions inlined and FTYPEs generated would spare us from writing those declarations on our own.

The attached patch contains a proposal that we would like to share. Please, let us know about any modification necessary that would make this patch useful for a larger community.

FYI: We have tested the patch against about a hundredth open-source Lisp projects.

Kindly,