Change wxWakeUpPipe to be a wxEventLoopSourceHandler.

No real changes but use wxEventLoopSource::AddSourceForFD() instead of
wxFDIODispatcher::RegisterFD() for this pipe because this is the preferred way
and because it will allow reusing this class for wxExecute() purposes later.

See #10258.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74346 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/wakeuppipe.cpp

@@ -126,8 +126,4 @@ void wxWakeUpPipe::OnReadWaiting()
     // The pipe is empty now, so future calls to WakeUp() would need to write
     // to it again.
     m_pipeIsEmpty = true;
-
-    // writing to the wake up pipe will make wxConsoleEventLoop return from
-    // wxFDIODispatcher::Dispatch() it might be currently blocking in, nothing
-    // else needs to be done
 }