fix bz60 and bz61 - meta char feedback

60: getpos() doesn't report the offending keystroke accurately when
rejecting M-something as a movement keystroke while moving the cursor;
61: typing M-N as a command keystroke produces
 |Unknown command 'M-
 |                 '.
where the '.' on the second line clobbers the top line of the map.

I can't reproduce the first one without extending the altmeta hack
[a run-time option to treat two char sequence ESC c as M-c] to getpos()
and nh_poskey(), which I've done for testing but am not including here.

I can't reproduce the second as it's described, but M-^J produces
 |Unknown command 'M-
 |'.--More--
and this fixes that, with a general fix that applies to any meta char.

The diffs include some cleanup/groundwork for maybe extending altmeta.

doc/fixes36.1

@@ -29,10 +29,14 @@ negative intrinsic protection shouldn't confer MC=1, "you are warded" (not
 make a slight adjustment to the quickmimic() sense wording
 fix typo in passage 1 of The Colour of Magic
 falling asleep when reading dull spellbook ignored sleep resistance
+getpos() complaint about invalid movement keystroke didn't describe meta-chars
+	accurately
 
 
 Platform- and/or Interface-Specific Fixes
 -----------------------------------------
+tty: M-N gave "Unknown command 'M-" with "'." finishing the sentence on the
+	line below it, leaving bogus '.' displayed on the top row of the map
 unix/X11: in top level Makefile, some commented out definitions of VARDATND
 	misspelled pilemark.xbm (as pilemark.xpm)
 win32gui: getversionstring() was overflowing the provided Help About buffer