systemc: Add m_cur_val and m_new_val to sc_signal.

These members are referred to in one of the tests.

Change-Id: Iab0110a0e3acf627986664069622704f17b703a1
Reviewed-on: https://gem5-review.googlesource.com/11355
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/ext/channel/sc_signal.hh

@@ -158,6 +158,12 @@ class sc_signal : public sc_signal_inout_if<T>,
         sc_channel_warn_unimpl(__PRETTY_FUNCTION__);
     }
 
+    // These members which store the current and future value of the signal
+    // are not specified in the standard but are referred to directly by one
+    // of the tests.
+    T m_cur_val;
+    T m_new_val;
+
   private:
     // Disabled
     sc_signal(const sc_signal<T, WRITER_POLICY> &) :