Symbol set changes...

curses:
  S_tree (use plus-or-minus sign instead of accidental horizontal line);
  S_bars (switch from default '#' to not-equals sign);

DECgraphics:
  S_altar (switch from default '_' to 'pi');
  S_bars (switch from 'pi' to not-equals sign);

DECgraphics_2: get rid of this commented out set since its contents are
  now folded into DECgraphics.

(The IBMgraphics one is just whitespace; delete a <space> that precedes
a <tab>.)