Adding initial introspection FFI tests.
Adding virtual FFI accessors.
Allow linking clibs.c instead of including it.
Including local source files verbatim in FFI.
Moving huff includes to include dir.

--HG--
rename : opt/sexp-huff.c => include/chibi/sexp-huff.c
rename : opt/sexp-hufftabdefs.h => include/chibi/sexp-hufftabdefs.h
rename : opt/sexp-hufftabs.c => include/chibi/sexp-hufftabs.c
rename : opt/sexp-unhuff.c => include/chibi/sexp-unhuff.c
Renaming include files as .h.

--HG--
rename : include/chibi/sexp-huff.c => include/chibi/sexp-huff.h
rename : include/chibi/sexp-hufftabs.c => include/chibi/sexp-hufftabs.h
rename : include/chibi/sexp-unhuff.c => include/chibi/sexp-unhuff.h