'whatdoes' command and new file: dat/keyhelp

Make the whatdoes ('&' or '?f') command support the 'altmeta' option
for meta-characters generated by two character seqeunce 'ESC char'.
Also, make it be more descriptive when reporting "no such command"
by including the numeric value it operated on when failing to match
any command.  That might provide a way for us to get some extra
information when players report problems with odd keystrokes:  we ask
them to type such at the "what command?" prompt and then tell us what
numbers come up.

It's been given a help file to deal with assorted idiosyncracies
which can come up when querying what keys do.  Unfortunately that
ended up being way more verbose than intended.

Installation of the extra data file has only been done for Unix.
Other platforms will get "can't open file" if they respond with
'&' or '?' to the "what command?" prompt.  The command will still
work though, just without the extra text.

include/global.h

@@ -1,4 +1,4 @@
-/* NetHack 3.6	global.h	$NHDT-Date: 1450306170 2015/12/16 22:49:30 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.47 $ */
+/* NetHack 3.6	global.h	$NHDT-Date: 1465114189 2016/06/05 08:09:49 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.49 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -18,6 +18,7 @@
 #define RECORD "record"         /* file containing list of topscorers */
 #define HELP "help"             /* file containing command descriptions */
 #define SHELP "hh"              /* abbreviated form of the same */
+#define KEYHELP "keyhelp"       /* explanatory text for 'whatdoes' command */
 #define DEBUGHELP "wizhelp"     /* file containing debug mode cmds */
 #define RUMORFILE "rumors"      /* file with fortune cookies */
 #define ORACLEFILE "oracles"    /* file with oracular information */