Update CIO hooks to be more flexible.

Replace the one hook we had with two to avoid underscore issues.

* msp430/cio.c: Remove, replace with...
* msp430/cio.S: New, this.

libgloss/msp430/cio.S

@@ -0,0 +1,33 @@
+/*
+
+Copyright (c) 2014  Red Hat, Inc. All rights reserved.
+
+This copyrighted material is made available to anyone wishing to use, modify,
+copy, or redistribute it subject to the terms and conditions of the BSD
+License.   This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY expressed or implied, including the implied warranties
+of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  A copy of this license
+is available at http://www.opensource.org/licenses. Any Red Hat trademarks that
+are incorporated in the source code or documentation are not subject to the BSD
+License and may only be used or replicated with the express permission of
+Red Hat, Inc.
+
+*/
+#include "memmodel.h"
+
+	.data
+
+	.global	__CIOBUF__
+__CIOBUF__:
+	.global	_CIOBUF_
+_CIOBUF_:
+	.space	75
+
+	.text
+
+	.global	_libgloss_cio_hook
+_libgloss_cio_hook:
+	.global C$$IO$$
+C$$IO$$:
+	nop
+        ret_