Add fid handling. Add function to read a 9p message
Tag handling
Add putheader to write the header of a 9p message
Change putstr to return the number of bytes inserted in the message.
Add getqid to create qids from userdata.
Add a qid field to a fid.
Add error handling, specially to readmsg.
Add pfid to print fids.
Add constante for message types.
Add open.