Topen
go fmt
Tread
Tclunk, fixed Topen and Tread

Handling Tclunk messages
TOpen now return the iounit for the client
TRead is fixed to return count 0 when the offset is too large
fixed Tread to handle io.EOF

When the Read call was able to read some data, and returned EOF, should
return the data from the file and not the EOF error, the next Tread will
catch the EOF.

When the Read call wasn't able to read data, but returned only EOF,
should return Count=0 to inform the client about the EOF.

Erros other than io.EOF, will trigger an Rerror response