xen: security and bugfix update (important)

XEN was updated to fix security issues and bugs. Security issues fixed: - bnc897657 - CVE-2014-7188: XSA-108 Improper MSR range used for x2APIC emulation - bnc895802 - CVE-2014-7156: XSA-106: Missing privilege level checks in x86 emulation of software interrupts - bnc895799 - CVE-2014-7155:...