ifdef cleanup, part 4a: '#ifdef undef'

This removes all code surrounded by '#ifdef undef'
One case is left: memmove() replaced by open-coded for loop,
in crypto/stack/stack.c  That needs further review.

Also removed a couple of instances of /* dead code */ if I saw them
while doing the main removal.

Reviewed-by: Matt Caswell <matt@openssl.org>