Use fixed-width types in the memory event interface

Use fixed-width types in the memory event interface

Set the types in the public memory_event header file to use
fixed-sized and self-aligned fields rather than "unsigned long".  AIUI
this feature only works with 64-bit hypervisors but I think this
change will be necessary to use 32-on-64 dom0 tools.

This breaks compatibility with older builds of the tools, but I can't
see any way to avoid it short of __attribute__((__packed__)).

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
Acked-by: Patrick Colp <pjcolp@cs.ubc.ca>