Make options lists instead of strings and make -append more magical

[Ryan Schmidt]

On Oct 8, 2013, at 14:07, Ryan Schmidt wrote:

> Trying to include options within a portfile has also been problematic. For example sometimes I seem to have to use join or eval to get things to work without Tcl inserting incorrect escaping.

For example I don't understand why in this commit I had to use eval to set destroot.env but not to set destroot.args:

https://trac.macports.org/changeset/112093