backport of fix for non-unicode, stl-enable

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_9_0_BRANCH@60780 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/fs_mem.cpp

@@ -186,9 +186,13 @@ void wxMemoryFSHandlerBase::AddFileWithMimeType(const wxString& filename,
                                                 const wxString& textdata,
                                                 const wxString& mimetype)
 {
-    AddFileWithMimeType(filename,
+    AddFileWithMimeType
-                        (const void*) textdata.mb_str(), textdata.length(),
+    (
-                        mimetype);
+        filename,
+        static_cast<const char *>(textdata.To8BitData()),
+        wxStrlen(static_cast<const char *>(textdata.To8BitData())),
+        mimetype
+    );
 }