Fixing cpplint issues.

Author: marek-trtik

src/taint-slicer/instrumentation_props.cpp

@@ -274,8 +274,9 @@ void taint_build_instrumentation_props(
           if(functions.count(node.get_function_id())!=0UL)
           {
             goto_programt::instructiont const&  I=*node.get_instruction_id();
-            assert(I.type==FUNCTION_CALL);
-            assert(to_code_function_call(I.code).function().id()==ID_symbol);
+            INVARIANT(I.type==FUNCTION_CALL, "");
+            INVARIANT(to_code_function_call(I.code).function().id()==ID_symbol,
+              "It must be a call via function identifier.");
             const std::string full_function_name=as_string(to_symbol_expr(
               to_code_function_call(I.code).function()).get_identifier());
             if(callees.count(full_function_name)!=0UL &&