(eventual) support for NFS servers without race conditions!

This means no NFS between nodes and ops/fs. There are still NFS mounts of
ops on boss however.

Added new defs-* variable NOSHAREDFS, which when set non-zero will disable
the export of NFS filesystems to nodes.  Involved lots of little changes:

 * /users, /proj, and /share filesystems are not exported to nodes.

 * Returned mount info now includes an FSTYPE key which will be set to "LOCAL"
   if NOSHAREDFS is in effect (by default it is set to "NFS-RACY"; more on
   this later).  In the case where it is set to LOCAL, the other mount lines
   no longer contain REMOTE=foo settings.  Because of this change,
   THE TMCD VERSION NUMBER HAS BEEN BUMPED TO 32.

 * The client rc.mounts script will now create local versions of /users/*,
   /proj/<pid>, and /share when FSTYPE=LOCAL.  It first runs mkextrafs to
   create a large partition for these, since someday we will likely want
  ...