wxDateTime starting to work, more tests for it and for threads in console sample

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@4779 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/string.cpp

@@ -203,7 +203,10 @@ extern int WXDLLEXPORT wxVsnprintf(wxChar *buf, size_t len,
     // vsnprintf() will not terminate the string with '\0' if there is not
     // enough place, but we want the string to always be NUL terminated
     int rc = wxVsnprintfA(buf, len - 1, format, argptr);
-    buf[len] = 0;
+    if ( rc == -1 )
+    {
+        buf[len] = 0;
+    }
 
     return rc;
 #endif // Unicode/ANSI