Stop having Unix defaults in Configure (partial)

Default values belong in the DEFAULT config target template, in
Configurations/00-base-templates.conf.

This isn't a complete move, but takes care of the most blatant
examples.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5177)