Added Boost.Predef to check environment such as endian.

https://github.com/boostorg/predef.git has been added as a submodule on
external/boost/predef.

In order to avoid macro name conflicts, replaced "BOOST_" with "MSGPACK_"
and "boost/" with "msgpack/" then copy replaced files to include/msgpack.
This process is described in CMakeLists.txt.
Replaced files are included as a part of msgpack-c. So you don't need to
do the converting process each time.

Fixed endian checking logic.

include/msgpack/predef/architecture/sparc.h

@@ -0,0 +1,55 @@
+/*
+Copyright Rene Rivera 2008-2014
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at
+http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+#ifndef MSGPACK_PREDEF_ARCHITECTURE_SPARC_H
+#define MSGPACK_PREDEF_ARCHITECTURE_SPARC_H
+
+#include <msgpack/predef/version_number.h>
+#include <msgpack/predef/make.h>
+
+/*`
+[heading `MSGPACK_ARCH_SPARC`]
+
+[@http://en.wikipedia.org/wiki/SPARC SPARC] architecture.
+
+[table
+    [[__predef_symbol__] [__predef_version__]]
+
+    [[`__sparc__`] [__predef_detection__]]
+    [[`__sparc`] [__predef_detection__]]
+
+    [[`__sparcv9`] [9.0.0]]
+    [[`__sparcv8`] [8.0.0]]
+    ]
+ */
+
+#define MSGPACK_ARCH_SPARC MSGPACK_VERSION_NUMBER_NOT_AVAILABLE
+
+#if defined(__sparc__) || defined(__sparc)
+#   undef MSGPACK_ARCH_SPARC
+#   if !defined(MSGPACK_ARCH_SPARC) && defined(__sparcv9)
+#       define MSGPACK_ARCH_SPARC MSGPACK_VERSION_NUMBER(9,0,0)
+#   endif
+#   if !defined(MSGPACK_ARCH_SPARC) && defined(__sparcv8)
+#       define MSGPACK_ARCH_SPARC MSGPACK_VERSION_NUMBER(8,0,0)
+#   endif
+#   if !defined(MSGPACK_ARCH_SPARC)
+#       define MSGPACK_ARCH_SPARC MSGPACK_VERSION_NUMBER_AVAILABLE
+#   endif
+#endif
+
+#if MSGPACK_ARCH_SPARC
+#   define MSGPACK_ARCH_SPARC_AVAILABLE
+#endif
+
+#define MSGPACK_ARCH_SPARC_NAME "SPARC"
+
+#include <msgpack/predef/detail/test.h>
+MSGPACK_PREDEF_DECLARE_TEST(MSGPACK_ARCH_SPARC,MSGPACK_ARCH_SPARC_NAME)
+
+
+#endif