Use wxDELETE() and wxDELETEA() when possible.

Use wxDELETE[A]() functions which automatically NULL out their arguments after
deleting them instead of doing it manually.

Closes #9685.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64656 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/exec/exec.cpp

@@ -1370,8 +1370,7 @@ void MyPipeFrame::OnProcessTerm(wxProcessEvent& WXUNUSED(event))
 {
     DoGet();
 
-    delete m_process;
-    m_process = NULL;
+    wxDELETE(m_process);
 
     wxLogWarning(wxT("The other process has terminated, closing"));