Log Message:
Update xenkernel45 and xentools45 to 4.5.5.
Changes since 4.5.3: mostly bugfixes, including fixes for
security issues XSA-172, XSA-173, XSA-175, XSA-176, XSA-178, XSA-179, XSA-180,
XSA-181, XSA-182, XSA-183, XSA-184, XSA-185, XSA-186 and XSA-187.
All but XSA-175 were already fixed in pkgsrc.
Complete list of changes and links to the XSA advisories:
https://www.xenproject.org/downloads/xen-archives/xen-45-series/xen-455.html