added wxString::[w]char_str() to 2.8 for forward compatibility with wx3

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@45213 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -836,6 +836,14 @@ public:
     // identical to c_str(), for MFC compatibility
     const wxChar* GetData() const { return c_str(); }
 
+    // conversion to *non-const* multibyte or widestring buffer; modifying
+    // returned buffer won't affect the string, these methods are only useful
+    // for passing values to const-incorrect functions
+    wxWritableCharBuffer char_str() const { return mb_str(wxConvLibc); }
+#if wxUSE_WCHAR_T
+    wxWritableWCharBuffer wchar_str() const { return wc_str(wxConvLibc); }
+#endif
+
     // conversion to/from plain (i.e. 7 bit) ASCII: this is useful for
     // converting numbers or strings which are certain not to contain special
     // chars (typically system functions, X atoms, environment variables etc.)