- Add fixed attribute, defaulting to FALSE
- QA: WS
- Refactor to develop the "correct" fix for xp-framework/xp-framework#278
  . Change TdsRecord::unmarshal() signature to include record mappings as last parameter
  . Pass record mappings to unmarshal() call from TdsProtocol
  . Change TdsV7 and common records to check for "len" member in field and not read that
  . Change T_VARIANT handle to delegate back to record mappings
  . Add special case handling for T_NUMERIC inside T_VARIANT handler
# TODO: Run integration tests