runmode option

<Someone>'s submittal of his `showrun' option has goaded
me to finally finish something I tried to implement some time back.
This adds a new run-time option called "runmode" which gives the
user control over how much screen udpating takes place during run
and travel movement.  It has four settings:
  teleport - update the map after movement has finished (this is
	the old behavior and also <Someone>'s !showrun behavior);
  run - update the map periodically (this is the new default);
	it uses (`moves' mod 7) to control the updating; it may
	need to have its own counter so that the updates are
	sync'd with the start of current movement rather than
	with `moves', but perhaps that won't matter;
  walk - update the map after each step (this is the behavior
	when <Someone>'s showrun is enabled);
  crawl - like walk, but with a longer delay after each step.

This option won't work well on configurations where delay_output()
doesn't produce a pause of reasonable duration, but I don't think
there's much we can do about that.

     The option setting ought to be stored in struct flags so that
it's maintained across save/restore cycles, but I put it into the
iflags structure with the other new options so that it won't cause
3.4.0 save files to be invalidated.

     I can't test the changes to Guidebook.mn; the corresponding
changes to Guidebook.tex process ok and don't show any obvious
glitches when viewed with xdvi.

doc/fixes34.1

@@ -207,6 +207,7 @@ msdos: compiling without NO_TERMS resulted in a link-time error
 General New Features
 --------------------
 lootabc option
+runmode option
 showrace option
 travel option
 mouse_support wincap option