Use qualified call to static member function.

Maybe this convinces gcc-5 to find the name.

dune/functions/functionspacebases/istlvectorbackend.hh

@@ -187,7 +187,7 @@ class ISTLVectorBackend
       // Here we'd simply like to call resize(c[i], sizeProvider, prefix);
       // but gcc does not accept this due to a bug. Instead it reports
       // "error: ‘this’ was not captured for this lambda function"
-      forwardToResize(c[i], sizeProvider, prefix);
+      ISTLVectorBackend<V>::forwardToResize(c[i], sizeProvider, prefix);
     });
   }