security/shibboleth-sp: update to 3.4.0

This is a minor update containing a new setting suggested by a
contributor (thus the unplanned minor version change) controlling
retries when TCP connections to shibd are used. The other changes are
minimal in nature.

Update the toolchain as well:

devel/xmltooling
textproc/xerces-c3

and bump PORTREVISION for security/opensaml due to dependencies'
updates.

Release notes: https://wiki.shibboleth.net/confluence/display/SP3/ReleaseNotes