[C++] add link to correct message header type

Author: Egor Seredin

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

@@ -1934,7 +1934,7 @@ private CharSequence generateMessageFlyweightCode(final String className, final
             "        std::uint64_t uint_value;\n" +
             "    };\n\n" +
 
-            "    using MessageHeader = %12$s;\n\n" +
+            "    using messageHeader = %12$s;\n\n" +
 
             "%11$s" +
             "    SBE_NODISCARD static SBE_CONSTEXPR %1$s sbeBlockLength() SBE_NOEXCEPT\n" +
@@ -1944,7 +1944,7 @@ private CharSequence generateMessageFlyweightCode(final String className, final
 
             "    SBE_NODISCARD static SBE_CONSTEXPR %1$s sbeBlockAndHeaderLength() SBE_NOEXCEPT\n" +
             "    {\n" +
-            "        return MessageHeader::encodedLength() + sbeBlockLength();\n" +
+            "        return messageHeader::encodedLength() + sbeBlockLength();\n" +
             "    }\n\n" +
 
             "    SBE_NODISCARD static SBE_CONSTEXPR %3$s sbeTemplateId() SBE_NOEXCEPT\n" +
@@ -1980,7 +1980,7 @@ private CharSequence generateMessageFlyweightCode(final String className, final
             "    %10$s &wrapAndApplyHeader(" +
             "char *buffer, const std::uint64_t offset, const std::uint64_t bufferLength)\n" +
             "    {\n" +
-            "        MessageHeader hdr(buffer, offset, bufferLength, sbeSchemaVersion());\n\n" +
+            "        messageHeader hdr(buffer, offset, bufferLength, sbeSchemaVersion());\n\n" +
 
             "        hdr\n" +
             "            .blockLength(sbeBlockLength())\n" +
@@ -1990,7 +1990,7 @@ private CharSequence generateMessageFlyweightCode(final String className, final
 
             "        return *this = %10$s(\n" +
             "            buffer,\n" +
-            "            offset + MessageHeader::encodedLength(),\n" +
+            "            offset + messageHeader::encodedLength(),\n" +
             "            bufferLength,\n" +
             "            sbeBlockLength(),\n" +
             "            sbeSchemaVersion());\n" +