Fix misbehavior of TranslatableString::Format in Windows build...

... Make sure it doesn't try to capture this (quite unnecessarily!) but calls
the static overload of DoFormat.

Make other qualified calls too for added measure.

src/Internat.cpp

@@ -356,13 +356,13 @@ TranslatableString &TranslatableString::Join(
       -> wxString {
       switch ( request ) {
          case Request::Context:
-            return DoGetContext( prevFormatter );
+            return TranslatableString::DoGetContext( prevFormatter );
          case Request::Format:
          case Request::DebugFormat:
          default: {
             bool debug = request == Request::DebugFormat;
             return
-               DoFormat( prevFormatter, str, debug )
+               TranslatableString::DoFormat( prevFormatter, str, debug )
                   + separator
                   + arg.DoFormat( debug );
          }