[DynInst_API:] [dyninst/dyninst] aa0880: Correct interpretation of Intel instructions requires

[Bolo -- Josef Burger <noreply@xxxxxxxxxx>]

  Branch: refs/heads/bolo/x86_immed
  Home:   https://github.com/dyninst/dyninst
  Commit: aa088045d3721819b705f6505608bd229dbc64d1
      https://github.com/dyninst/dyninst/commit/aa088045d3721819b705f6505608bd229dbc64d1
  Author: Bolo <bolo@xxxxxxxxxxx>
  Date:   2023-02-16 (Thu, 16 Feb 2023)

  Changed paths:
    M common/src/arch-x86.h
    M instructionAPI/h/Result.h

  Log Message:
  -----------
  Correct interpretation of Intel instructions requires
sign extension.   On intel it works because chars are
signed on that platform.   On other platforms (arm64, powerpc64)
intel code was not correctly analyzed because incorrect
values were generated from 8 bit immediate constants;
which were interpreted as unsigned on those systems.

These changes ensure intel code will be correctly interpreted
on any system, regardless of the signedness of chars.

A n-way validation was used to validate this change, to
ensure that correct code interpretation of (intel, arm,
power) code happens on all three platforms.    No other
issues of this nature were located -- at this time.