QPixmapFilter will live in QtWidgets

The class is only used for QGraphicsEffect. When merging
QtOpenGL into Gui and Widgets, the GL nased pixmap
filters will also need to be moved into effects/ and
the pixmapFilter() method in QPaintEngineEx can get
removed.

src/gui/effects/effects.pri

@@ -1,4 +1,6 @@
 HEADERS += effects/qgraphicseffect.h \
-    effects/qgraphicseffect_p.h
+    effects/qgraphicseffect_p.h \
+        effects/qpixmapfilter_p.h
 
-SOURCES += effects/qgraphicseffect.cpp
+SOURCES += effects/qgraphicseffect.cpp \
+        effects/qpixmapfilter.cpp

src/gui/image/image.pri

@@ -23,7 +23,6 @@ HEADERS += \
         image/qpixmapcache_p.h \
         image/qpixmapdata_p.h \
         image/qpixmapdatafactory_p.h \
-        image/qpixmapfilter_p.h \
         image/qimagepixmapcleanuphooks_p.h \
         image/qvolatileimage_p.h \
         image/qvolatileimagedata_p.h \
@@ -42,7 +41,6 @@ SOURCES += \
         image/qpixmapcache.cpp \
         image/qpixmapdata.cpp \
         image/qpixmapdatafactory.cpp \
-        image/qpixmapfilter.cpp \
         image/qmovie.cpp \
         image/qpixmap_raster.cpp \
         image/qpixmap_blitter.cpp \

src/gui/painting/qpaintengineex_p.h

@@ -212,6 +212,7 @@ public:
     virtual void beginNativePainting() {}
     virtual void endNativePainting() {}
 
+    // ### Qt5: remove, once QtOpenGL is merged into QtGui and QtWidgets
     // Return a pixmap filter of "type" that can render the parameters
     // in "prototype".  The returned filter is owned by the engine and
     // will be destroyed when the engine is destroyed.  The "prototype"