Configure: maintain compability with pre-"make variables" Configure

There were a few environment variables that we supported in earlier
Configure versions which got transfered to the %user table.  This
change makes sure that we still support them, by simply pre-populating
the corresponding %user entries with those environment values.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5641)