Configure: use 5.10.0, don't require...

Configure started with 'require 5.10.0', but if executed by older perl
it failed with "might be runaway multi-line // string" instead of
naturally expected "Perl v5.10.0 required--this is only v5.x.y".

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit d83112b7)