rlc: Start to move things out of the tbf into the rlc

Add remarks of possible broken behavior inside the tbf
routines. Move the preparation (and init) into the new
rlc.cpp file.
diff --git a/src/rlc.cpp b/src/rlc.cpp
new file mode 100644
index 0000000..4319c49
--- /dev/null
+++ b/src/rlc.cpp
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2013 by Holger Hans Peter Freyther
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include "tbf.h"
+
+extern "C" {
+#include <osmocom/core/utils.h>
+}
+
+
+uint8_t *gprs_rlc_data::prepare(size_t block_data_len)
+{
+	/* todo.. only set it once if it turns out to be a bottleneck */
+	memset(block, 0x0, ARRAY_SIZE(block));
+	memset(block, 0x2b, block_data_len);
+
+	return block;
+}