write v2.1 README file.

write v2.1 _requires_ at least GNO v2.0.5 or the multi-user update.

What's changed:
   - changed error messages to go to stderr (previously to stdout).
   - added several checks on ut_type to insure validation of utmp entry and
     not write to entries marked UT_INVISIBLE.
   - fixed bug which would have caused problems in an fputs() command iff
     the length of the line name was the maximum allowed.
   - have it on authority that the CRs appended to the ends of the output
     lines will be correctly translated.  This was questionable when 2.0 was
     sent out.

Special thanks to Phil Vandry again for suggestions - he sent me source after
the MU upgrade, but it got corrupted.  He sent me a new copy, and I used it to
modify the new code.  Thanks :-)

Please send all requests to:
America On-Line: WDPhoenix (@aol.com)
Delphi:          WDPHOENIX (@delphi.com)
US Snail:        Les Barstow
                 275 Route 10 East
                 Suite 220-136
                 Succasunna, NJ 07876
