Also escape call number in responses

Also escape call number value in XML responses.

Still a strong desire to move away from heredocs for generating xml.

Signed-off-by: Jeff Godin <jgodin@tadl.org>
Don't use HTML entities in XML

Not all HTML entities are valid (built-in) XML entities. Don't try
to use HTML entities in XML.

Instead (until the TODO of "Move away from heredocs for generating
XML" is completed), use a naive sub to replace only ampersand,
greater than, and less than.

Signed-off-by: Jeff Godin <jgodin@tadl.org>
Merge pull request #9 from tadl/xml_escaping_fixes

xml escaping fixes

In addition to title and author, also attempt to escape call number
values in ItemRequestedResponse messages.

Also, don't use HTML::Entities::encode as that can introduce HTML
entities which are not valid built-in XML entities.

Signed-off-by: Jeff Godin <jgodin@tadl.org>