Right now, the data in a guid element is stored in the
appropriate item's hash. However, the isPermaLink
attribute is not stored.
This patch sets a 'permaLink' key to each element that
has a guid. If the isPermaLink attribute is set to 'false',
permaLink is set to 0. If it's absent or set to something
besides false, permaLink is set to 1.
permaLink is used instead of a different name because
that's what's referred to on line 1225 of the unpatched
version 1.22, in &as_rss_2_0.