Bug found by:

Bug found by:
Submitted by:
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Import of several changes from a private tree:

- Implement canvas (re)sizing;

- Implement canvas zooming;

- Implement several synthetic topology generators (chain, star,
  cycle, wheel, cube, clique, bipartite);

- Implement a procedure and GUI hooks for selecting adjacent nodes;

- Display a grid in the canvas;

- Change the cursor to a "watch" icon during undo / redo / delete
  operations;

- Link color and "thickness" can now be configured on individual
  link basis;

- Extensive (yet not complete) indentation cleanup - we should use
  modulo 4 tab stops exclusively;

- Enclose "expr" expressions in braces, per suggestion from manual
  pages for performance improvement (though it seems that no
  no improvements can be observed);

- Remove the "Configure remote hosts" menu, given that we are
  considering different approaches for executing remote experiments.
  The "nexec" and related procedures are left untouched for now;

- Adjust default window size to cover the entire default canvas
  surface, while is should still fit into 1024x768 displays.