Properly handle the case where QtWidgets is not available.

It does use a config test for now, just to make it clearer.  The Mac
backend currently requires widgets, but most of the others should work
without it (just not supporting QVideoWidget/WindowControl).

The QVideoDeviceControl interface was modified to remove the QIcon
usage - it was never implemented.

Unfortunately even the QML examples need widgets for the wrapper
application, and will need to be ported to QtGui based wrapper.

Change-Id: I8a55ad5cf09ab51749510bf16f49de0bd3f0bcdb
Reviewed-by: Ling Hu <ling.hu@nokia.com>

examples/examples.pro

@@ -1,22 +1,27 @@
 TEMPLATE = subdirs
 
-SUBDIRS += \
-    radio \
-    camera \
-    slideshow \
-    spectrum \
-    audiorecorder \
-    audiodevices \
-    audioinput \
-    audiooutput \
-    videographicsitem \
-    videowidget \
-    video \
-    player \
+# These examples all need widgets for now (using creator templates that use widgets)
+contains(config_test_widgets, yes) {
+    SUBDIRS += \
+        radio \
+        camera \
+        slideshow \
+        spectrum \
+        audiorecorder \
+        audiodevices \
+        audioinput \
+        audiooutput \
+        videographicsitem \
+        videowidget \
+        player
 
-contains(QT_CONFIG, declarative) {
-    disabled:SUBDIRS += declarative-camera
-    SUBDIRS += declarative-radio
+    contains(QT_CONFIG, declarative) {
+        disabled:SUBDIRS += declarative-camera
+        SUBDIRS += \
+            declarative-radio \
+            video
+    }
+
+    QT += widgets
 }
 
-QT+=widgets