centralize and fixup example sources install targets

This follows suit with aeb036e in qtbase.

Change-Id: Ie8580d0a1f38ab9858b0e44c9f99bdc552a1752a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: hjk <qthjk@ovi.com>

examples/examples.pro

@@ -1,31 +1,3 @@
 TEMPLATE = subdirs
-
-SUBDIRS += audiodecoder
-
-# These examples all need widgets for now (using creator templates that use widgets)
-!isEmpty(QT.widgets.name) {
-    SUBDIRS += \
-        radio \
-        camera \
-        spectrum \
-        audiorecorder \
-        audiodevices \
-        audioinput \
-        audiooutput \
-        videographicsitem \
-        videowidget \
-        player \
-        customvideosurface
-
-    QT += widgets
-}
-
-!isEmpty(QT.gui.name):!isEmpty(QT.qml.name) {
-    disabled:SUBDIRS += declarative-camera
-    SUBDIRS += \
-        declarative-radio \
-        video
-}
-
-config_openal: SUBDIRS += audioengine
+SUBDIRS += multimedia multimediawidgets