<<< Breaking change >>>
In the functions unpack() and parse(),
Old behavior: If any parse error is happend, offset is NOT updated.
New behavior: If any parse error is happend, offset is updated to the
position the error happened.
It helps MessagePack format error analysis.
If you want to old behavior, copy the original value of offset and then call unpack()
and/or parse().
The parameter 'offset' of unpack() function family, not unpacker family, updates only when the function successfully finished.
The parameter 'offset' used to update even if a caller passes insufficient bytes to the unpack() function family.
