NewServer with callbacks based on functional options for friendly APIs.
Replaces NewUFS. Add .Debug() to return a Debug-enabled version of the
FileServer.

Remove -root and -debug flags, use functional options instead.

Most likely will conflict with Harvey-OS#32.

Based on NewServer rather than NewUFS.

Use NewServer rather than NewUFS.

Add debug.Server which wraps a NineServer and logs before and after
calling functions for the underlying server. Add Trace option to
protocol.Server.

Makes Harvey-OS#34 obsolete

Sloppy merge, should have tested build afterwards.

Server.Trace was replaced by Trace option.

Set trace for the various servers to no-op log by default. Users can
then change the trace function using the Trace option.

Should not be nil otherwise the *.Trace will return an error.

Forgot to s/File/file.