If we pass CHECK_CONS(), we don't need CONSP()s in Fcar() and Fcdr() and may use XCAR()
and XCDR() instead.

Dmitry

P.S. Is code size the only reason to call Fcar(), Fcdr() and their safe versions directly
from C code ? Replacing these dumb proxies with an appropriate macros eliminates a lot of
function calls at the cost of ~28K increment in code size (for a stripped binary on x86).
Note if someone needs smaller emacs executable (what a strange requirement, but why not ?),
just replacing -O2 with -Os saves ~235K.

P.P.S. Maintainers, please update my e-mail to dmantipov@yandex.ru in src/ChangeLog -
dmitry.antipov@mail.ru is no longer used.