[c++] Add in missing bufferLength initialisation for copy constructors. Issue #513.

Author: mjpt777

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

@@ -1280,10 +1280,16 @@ private static CharSequence generateFixedFlyweightCode(final String className, f
             "        reset(buffer, 0, bufferLength, actingVersion);\n" +
             "    }\n\n" +
             "    %1$s(const %1$s& codec) :\n" +
-            "        m_buffer(codec.m_buffer), m_offset(codec.m_offset), m_actingVersion(codec.m_actingVersion){}\n\n" +
+            "        m_buffer(codec.m_buffer),\n" +
+            "        m_offset(codec.m_offset),\n" +
+            "        m_bufferLength(codec.m_bufferLength),\n" +
+            "        m_actingVersion(codec.m_actingVersion){}\n\n" +
             "#if __cplusplus >= 201103L\n" +
             "    %1$s(%1$s&& codec) :\n" +
-            "        m_buffer(codec.m_buffer), m_offset(codec.m_offset), m_actingVersion(codec.m_actingVersion){}\n\n" +
+            "        m_buffer(codec.m_buffer),\n" +
+            "        m_offset(codec.m_offset),\n" +
+            "        m_bufferLength(codec.m_bufferLength),\n" +
+            "        m_actingVersion(codec.m_actingVersion){}\n\n" +
             "    %1$s& operator=(%1$s&& codec) SBE_NOEXCEPT\n" +
             "    {\n" +
             "        m_buffer = codec.m_buffer;\n" +