trace: improve usefulness of hypercall trace record

trace: improve usefulness of hypercall trace record

Trace hypercalls using a more useful trace record format.

The EIP field is removed (it was always somewhere in the hypercall
page) and include selected hypercall arguments (e.g., the number of
calls in a multicall, and the number of PTE updates in an mmu_update
etc.).  12 bits in the first extra word are used to indicate which
arguments are present in the record and what size they are (32 or
64-bit).

This is an incompatible record format so a new event ID is used so
tools can distinguish between the two formats.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Committed-by: Keir Fraser <keir@xen.org>