codec: json: encodeFloat no longer inspects bytes to see if .0 to be added
codec: json: encodeFloat no longer inspects bytes to see if .0 to be added

Instead, we look at the float value and determine if to set precision
to 1 so that .0 will be added.

Also, rearrange json(En|De)cDriver structs for better cache coherency.

ugorji/go,ugorji/go,ugorji/go