1. changed all "wxMBConv& conv" parameters to "const wxMBConv&"

2. this allows to use wxConvAuto() instead of wxConvUTF8 as default value
   for this parameter in the classes which read text from the file: wxConvAuto
   automatically recognizes the BOM at the start of file and uses the correct
   conversion
3. don't use Windows for UTF-7 conversions as there is no way to make it
   fail on invalid UTF-7 strings; use our own wxMBConvUtf7 instead


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38570 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/txtstrm.cpp

@@ -35,7 +35,9 @@
 // ----------------------------------------------------------------------------
 
 #if wxUSE_UNICODE
-wxTextInputStream::wxTextInputStream(wxInputStream &s, const wxString &sep, wxMBConv& conv)
+wxTextInputStream::wxTextInputStream(wxInputStream &s,
+                                     const wxString &sep,
+                                     const wxMBConv& conv)
   : m_input(s), m_separators(sep), m_conv(conv)
 {
     memset((void*)m_lastBytes, 0, 10);
@@ -298,7 +300,9 @@ wxTextInputStream& wxTextInputStream::operator>>(float& f)
 
 
 #if wxUSE_UNICODE
-wxTextOutputStream::wxTextOutputStream(wxOutputStream& s, wxEOL mode, wxMBConv& conv)
+wxTextOutputStream::wxTextOutputStream(wxOutputStream& s,
+                                       wxEOL mode,
+                                       const wxMBConv& conv)
   : m_output(s), m_conv(conv)
 #else
 wxTextOutputStream::wxTextOutputStream(wxOutputStream& s, wxEOL mode)