Refactor config - a small cosmetic touchup of Configure

Start simple, removed some unused variables and change all '<<EOF' to
'<<"EOF"'.  The latter is because some code colorizers (notably, in
emacs) cannot recognise the here document end marker unless it's
quoted and therefore assume the rest of the file is part of the here
document.

Reviewed-by: Rich Salz <rsalz@openssl.org>