[c++] Add SBE_NOEXCEPT to bufferLength accessor method after merge.

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java

@@ -1300,7 +1300,7 @@ private static CharSequence generateFixedFlyweightCode(final String className, f
             "    {\n" +
             "        return m_buffer;\n" +
             "    }\n\n" +
-            "    std::uint64_t bufferLength() const\n" +
+            "    std::uint64_t bufferLength() const SBE_NOEXCEPT\n" +
             "    {\n" +
             "        return m_bufferLength;\n" +
             "    }\n\n",