www/aws: Update to from version 2.10.0 to 3.1.0

There is no dedicated change log but version 2.10 was introduced to
pkgsrc 2.5 years ago.  The current capability is described by
http://docs.adacore.com/aws-docs/aws.html

This is roughly equivalent to Adacore release 2013 of aws.
The "gnutls" option was added as an alternative to ssl.
www/aws-demos: Follow update of www/aws

The www/aws-demos builds off of www/aws, but it required several changes
after www/aws was updated to version 3.1.0.

Five new demos were also added.