C++ front-end: parameter symbols are file- and thread-local

As global symbols they wouldn't be amenable to constant propagation in
multi-threaded contexts.

Author: tautschnig

src/cpp/cpp_typecheck_function.cpp

@@ -41,17 +41,15 @@ void cpp_typecheckt::convert_parameter(
   if(!lookup(identifier, check_symbol))
     return;
 
-  symbolt symbol;
+  parameter_symbolt symbol;
 
   symbol.name=identifier;
   symbol.base_name=parameter.get_base_name();
   symbol.location=parameter.source_location();
   symbol.mode = current_mode;
   symbol.module=module;
   symbol.type=parameter.type();
-  symbol.is_state_var=true;
   symbol.is_lvalue=!is_reference(symbol.type);
-  symbol.is_parameter=true;
 
   INVARIANT(!symbol.base_name.empty(), "parameter has base name");