At least for the Bochs backend there might be side effects when saving
the simulator state while tracing, which therefore should be avoided.
As there is no known use-case for using a --save-symbol different to
--start-symbol, this change disables the semantics behind
--save-symbol completely and only keeps the command-line switch for
backward compatibility reasons (existing automatic test scripts etc.).
The generic-tracing experiment now complains and aborts if a
--save-symbol different to --start-symbol is given.
Change-Id: I6072d846be96e016534cc83db375a400cfc25303
b6fc98abae