Make directshow-plugin available.

No longer include <qedit.h> in directshow-plugin,
which no longer ships in newer SDKs.

Ensure it only provides the camera service if the
WMF-plugin is built by using a different .json-file.

Adapt qcamerabackend-test to use widgets.

Task-number: QTBUG-28047

Change-Id: I22ea441b9edb56ff55bc275dba37c01c77d8dd90
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

config.tests/directshow/main.cpp

@@ -43,13 +43,6 @@
 #include <d3d9.h>
 #include <vmr9.h>
 
-#pragma include_alias("dxtrans.h","qedit.h")
-#define __IDxtCompositor_INTERFACE_DEFINED__
-#define __IDxtAlphaSetter_INTERFACE_DEFINED__
-#define __IDxtJpeg_INTERFACE_DEFINED__
-#define __IDxtKey_INTERFACE_DEFINED__
-#include <qedit.h>
-
 int main(int, char**)
 {
     return 0;