combase: Add RoGetActivationFactory stub.

dlls/api-ms-win-core-winrt-l1-1-0/api-ms-win-core-winrt-l1-1-0.spec

 @ stub RoActivateInstance
-@ stub RoGetActivationFactory
+@ stdcall RoGetActivationFactory(ptr ptr ptr) combase.RoGetActivationFactory
 @ stub RoGetApartmentIdentifier
 @ stdcall RoInitialize(long) combase.RoInitialize
 @ stub RoRegisterActivationFactories

dlls/combase/combase.spec

@@ -248,7 +248,7 @@
 @ stub RoFailFastWithErrorContext
 @ stub RoFreeParameterizedTypeExtra
 @ stub RoGetActivatableClassRegistration
-@ stub RoGetActivationFactory
+@ stdcall RoGetActivationFactory(ptr ptr ptr)
 @ stub RoGetAgileReference
 @ stub RoGetApartmentIdentifier
 @ stub RoGetErrorReportingFlags

dlls/combase/roapi.c

@@ -18,6 +18,7 @@
 
 #include "objbase.h"
 #include "roapi.h"
+#include "hstring.h"
 
 #include "wine/debug.h"
 
@@ -45,3 +46,12 @@ void WINAPI RoUninitialize(void)
 {
     CoUninitialize();
 }
+
+/***********************************************************************
+ *      RoGetActivationFactory (combase.@)
+ */
+HRESULT WINAPI RoGetActivationFactory(HSTRING classid, REFIID iid, void **factory)
+{
+    FIXME("stub: %p %p %p\n", classid, iid, factory);
+    return E_NOTIMPL;
+}