gracefully kill htif thread, fixing tty stuff

csrc/emulator.cc

@@ -176,6 +176,8 @@ int main(int argc, char** argv)
   if (vcd)
     fclose(vcdfile);
 
+  delete htif;
+
   if (failure)
   {
     fprintf(logfile, "*** FAILED *** (%s) after %lld cycles\n", failure, (long long)trace_count);

csrc/vcs_main.cc

@@ -101,6 +101,11 @@ void htif_init
   htif = new htif_emulator_t(args);
 }
 
+void htif_fini()
+{
+  delete htif;
+}
+
 void htif_tick
 (
   vc_handle htif_in_valid,