Sync and update ipi_x2apic test case.

This case cover test case "[x2APIC] measure overhead of IPI with and without x2apic"

Following two patch sync current internal code to upstream.
	 qemu: Add ipi_x2apic test case.
         qemu: Add pipetest.c script used in ipi_x2apic

Following patch are some update and bug fix during sync, will backport them to internal tree late.

	 qemu: Check x2apic flag after guest reboot 
         share: Format shared/scripts/pipetest.c script