generic-tracing: remove --save-symbol

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

src/experiments/generic-tracing/experiment.hpp

@@ -11,7 +11,6 @@
 class GenericTracing : public fail::ExperimentFlow {
 	std::string start_symbol;
 	std::string stop_symbol;
-	std::string save_symbol;
 
 	std::string state_file;
 	std::string trace_file;