Temporary fix for #65.

It looks like that when we use the `Simple` output module, we get
weird errors when trying to load state for any game, most likely due to
memory corruption. AFAIK, it seems the frame buffer is not large enough
to render all components.

This issues does not appear when using OpenGL, or using the Simple with
any display filter available.

src/wx/panel.cpp

@@ -31,6 +31,7 @@ GameArea::GameArea()
     , rewind_time(0)
     , do_rewind(false)
     , rewind_mem(0)
+    , num_rewind_states(0)
     , loaded(IMAGE_UNKNOWN)
     , basic_width(GBAWidth)
     , basic_height(GBAHeight)
@@ -1860,6 +1861,7 @@ void DrawingPanelBase::DrawArea(uint8_t** data)
                     showSpeedTransparent);
 
                 free(buf);
+                buf = NULL;
             } else
                 panel->osdtext.clear();
         }
@@ -1978,9 +1980,11 @@ void DrawingPanelBase::OnSize(wxSizeEvent& ev)
 DrawingPanelBase::~DrawingPanelBase()
 {
     // pixbuf1 freed by emulator
-    if (pixbuf2)
+    if (pixbuf1 != pixbuf2 && pixbuf2)
+    {
         free(pixbuf2);
-
+        pixbuf2 = NULL;
+    }
     InterframeCleanup();
 
     if (nthreads) {
@@ -2004,7 +2008,7 @@ BasicDrawingPanel::BasicDrawingPanel(wxWindow* parent, int _width, int _height)
     // 16 or 32, though
     if (gopts.filter == FF_NONE && gopts.ifb == IFB_NONE)
         // changing from 32 to 24 does not require regenerating color tables
-        systemColorDepth = 24;
+        systemColorDepth = 32;
     if (!did_init) DrawingPanelInit();
 }