No encodingOffset() method in MessageHeader.h

[kdoherty2]

SBE Tool v1.7.9

We cannot easily verify at compile time that the wire format of MessageHeader classes in different schema files is the same, because the no encodingOffset() method is generated in MessageHeader.h. (The generator allows for reordering of standard header fields, blockLength, templateId, schemaId, versionId.

All other classes in the schema file have encoding offset methods:

static SBE_CONSTEXPR std::size_t quantityEncodingOffset() SBE_NOEXCEPT
{ return 17; }