x86[_64] assembly pack: add Silvermont performance data.

Reviewed-by: Rich Salz <rsalz@openssl.org>
md5-x86_64.pl: work around warning.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Configure: add configuration for crypto/ec/asm extensions.

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