Add toggle extended command

Allows the user to configure a key binding to toggle any boolean
option, for example:

BIND=':toggle(price_quotes)
BIND=v:toggle(autodig)

The option must be settable in-game.

doc/Guidebook.mn

@@ -1754,6 +1754,18 @@ floor container menu.
 .lp ""
 Autocompletes.
 Default key is \(oqM-T\(cq.
+.lp "#toggle  "
+Toggle a boolean option on or off.
+Requires a parameter in parenthesis, the name of the option to toggle.
+The option must be settable in-game.
+.lp ""
+For example:
+.sd
+.ft CR
+BIND=':toggle(price_quotes)
+BIND=@:toggle(autopickup)
+.ft
+.ed
 .lp "#travel  "
 Travel to a specific location on the map.
 Default key is \(oq_\(cq. \" underscore

doc/Guidebook.tex

@@ -1826,6 +1826,21 @@ floor container menu.
 \\
 %.lp ""
 Autocompletes. Default key is `\texttt{M-T}'.
+%.lp
+\item[\#toggle]
+Toggle a boolean option on or off.
+Requires a parameter in parenthesis, the name of the option to toggle.
+The option must be settable in-game.
+
+%.lp ""
+For example:
+%.sd
+\begin{verbatim}
+    BIND=':toggle(price_quotes)
+    BIND=@:toggle(autopickup)
+\end{verbatim}
+%.ed
+
 %.lp
 \item[\#travel]
 Travel to a specific location on the map.

doc/fixes3-7-0.txt

@@ -2912,6 +2912,7 @@ the game now automatically tracks which sell prices and buy prices you have
 new shields: shield of shock resistance, shield of drain resistance
 new wand: wand of stasis
 early-game monsters always miss with their first use of an attack wand
+new command #toggle which can be used to toggle a boolean option
 
 
 Platform- and/or Interface-Specific New Features