[RFE] Add stacked registers to SAL records

[Keith Owens <kaos@sgi.com>]

SAL error records contain most registers in sal_processor_static_info,
but not the stacked registers.  What is the process for adding another
GUID to the SAL specification to contain the stacked registers?

Layout:

  number of stacked registers in this record
  cfm for frame at the time of failure
  stacked registers, ending with the cfm.sof registers

This GUID would be optional, if a particular SAL implementation did not
produce it then that platform would not have stacked registers printed
via salinfo.