Merge branch 'msvc-warns'

Fix an annoying MSVC warning in SDK headers.

Remove wxUSE_IOSTREAMH.

See https://github.com/wxWidgets/wxWidgets/pull/1614

samples/docview/doc.cpp

@@ -29,7 +29,7 @@
 #endif
 
 #if wxUSE_STD_IOSTREAM
-    #include "wx/ioswrap.h"
+    #include <iostream>
 #else
     #include "wx/txtstrm.h"
 #endif

samples/typetest/typetest.cpp

@@ -32,13 +32,8 @@
 #undef new
 #endif
 
-#include "wx/ioswrap.h"
-
-#if wxUSE_IOSTREAMH
-    #include <fstream.h>
-#else
-    #include <fstream>
-#endif
+#include <iostream>
+#include <fstream>
 
 #include "wx/wfstream.h"
 #include "wx/datstrm.h"

samples/widgets/textctrl.cpp

@@ -40,7 +40,6 @@
 #endif
 
 #include "wx/sizer.h"
-#include "wx/ioswrap.h"
 
 #include "widgets.h"