[C++] Add a constructor overload to composites that uses default schema version.

Author: denizevrenci

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

@@ -1560,6 +1560,12 @@ private CharSequence generateFixedFlyweightCode(final String className, final in
  " %1$s(buffer, 0, bufferLength, actingVersion)\n" +
  " {\n" +
  " }\n\n" +
+ " %1$s(\n" +
+ " char *buffer,\n" +
+ " const std::uint64_t bufferLength) :\n" +
+ " %1$s(buffer, 0, bufferLength, sbeSchemaVersion())\n" +
+ " {\n" +
+ " }\n\n" +
  " %1$s &wrap(char *buffer, const std::uint64_t offset, const std::uint64_t actingVersion," +
  " const std::uint64_t bufferLength)\n" +
  " {\n" +