Fix Segfault in final GC when using FXSplashWindow.

The internal object allocated when calling FXSplashWindow.new was FXSplashWindow instead
of FXRbSplashWindow, so that no FXRbUnregisterRubyObj() was called. Therefore the object
was double free'd.

Stacktrace was:
==11529== Invalid read of size 8
==11529==    at 0x9265BBC: FX::FXObject::getClassName() const (FXObject.cpp:280)
==11529==    by 0x862EE55: FXRbObject::freefunc(FX::FXObject*) (markfuncs.cpp:77)
==11529==    by 0x4EA6254: finalize_list (gc.c:2944)
==11529==    by 0x4EAAFC2: rb_gc_call_finalizer_at_exit (gc.c:3075)
==11529==    by 0x4E9773B: ruby_cleanup (eval.c:101)
==11529==    by 0x4E979C4: ruby_run_node (eval.c:244)
==11529==    by 0x4007FA: main (main.c:38)
==11529==  Address 0x75e24c0 is 0 bytes inside a block of size 248 free'd
==11529==    at 0x4C2A4BC: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11529==    by 0x92B98AD: FX::FXSplashWindow::~FXSplashWindow() (FXSplashWindow.cpp:219)
==11529==    by 0x917C990: FX::FXComposite::~FXComposite() (FXComposite.cpp:304)
==11529==    by 0x929A5EF: FX::FXRootWindow::~FXRootWindow() (FXRootWindow.cpp:209)
==11529==    by 0x929A621: FX::FXRootWindow::~FXRootWindow() (FXRootWindow.cpp:211)
==11529==    by 0x9156DB9: FX::FXApp::~FXApp() (FXApp.cpp:4994)
==11529==    by 0x84912F3: FXRbApp::~FXRbApp() (FXRbApp.cpp:118)
==11529==    by 0x8491347: FXRbApp::~FXRbApp() (FXRbApp.cpp:127)
==11529==    by 0x862EF8E: FXRbObject::freefunc(FX::FXObject*) (markfuncs.cpp:92)
==11529==    by 0x4EA6254: finalize_list (gc.c:2944)
==11529==    by 0x4EAAFC2: rb_gc_call_finalizer_at_exit (gc.c:3075)
==11529==    by 0x4E9773B: ruby_cleanup (eval.c:101)

ext/fox16/MANIFEST

@@ -148,6 +148,7 @@ include/FXRbShutter.h
 include/FXRbShutterVirtuals.h
 include/FXRbSlider.h
 include/FXRbSpinner.h
+include/FXRbSplashWindow.h
 include/FXRbSplitter.h
 include/FXRbStatusbar.h
 include/FXRbStatusline.h

ext/fox16/include/impl.h

@@ -166,6 +166,7 @@ FXRbIMPLEMENT(FXRbShutter,FXShutter,NULL,0)
 FXRbIMPLEMENT(FXRbShutterItem,FXShutterItem,NULL,0)
 FXRbIMPLEMENT(FXRbSlider,FXSlider,NULL,0)
 FXRbIMPLEMENT(FXRbSpinner,FXSpinner,NULL,0)
+FXRbIMPLEMENT(FXRbSplashWindow,FXSplashWindow,NULL,0)
 FXRbIMPLEMENT(FXRbSplitter,FXSplitter,NULL,0)
 FXRbIMPLEMENT(FXRbSpring,FXSpring,NULL,0)
 FXRbIMPLEMENT(FXRbStatusBar,FXStatusBar,NULL,0)

swig-interfaces/FXSplashWindow.i

@@ -52,11 +52,17 @@ public:
   long onPaint(FXObject*,FXSelector,void* PTR_EVENT);
 public:
 
-  /// Construct splash window
-  FXSplashWindow(FXApp* a,FXIcon* ic,FXuint opts=SPLASH_SIMPLE,FXuint ms=5000);
+  %extend {
+    /// Construct splash window
+    FXSplashWindow(FXApp* a,FXIcon* ic,FXuint opts=SPLASH_SIMPLE,FXuint ms=5000){
+      return new FXRbSplashWindow(a,ic,opts,ms);
+      }
 
-  /// Construct splash window
-  FXSplashWindow(FXWindow* own,FXIcon* ic,FXuint opts=SPLASH_SIMPLE,FXuint ms=5000);
+    /// Construct splash window
+    FXSplashWindow(FXWindow* own,FXIcon* ic,FXuint opts=SPLASH_SIMPLE,FXuint ms=5000){
+      return new FXRbSplashWindow(own,ic,opts,ms);
+      }
+    }
 
   /// Set the icon for the splash window
   void setIcon(FXIcon* ic);