fixed NextChar() to read the entire character at once as before it stopped on the first byte for ASCII input encoded as UTF-32LE

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38577 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/txtstrm.cpp

@@ -79,8 +79,8 @@ wxChar wxTextInputStream::NextChar()
         if(m_input.LastRead() <= 0)
             return wxEOT;
 
-        int retlen = (int) m_conv->MB2WC(wbuf, m_lastBytes, 2); // returns -1 for failure
-        if(retlen >= 0) // res == 0 could happen for '\0' char
+        if ( m_conv->ToWChar(wbuf, WXSIZEOF(wbuf), m_lastBytes, inlen + 1)
+                != wxCONV_FAILED )
             return wbuf[0];
     }
     // there should be no encoding which requires more than nine bytes for one character...