Accessibility: showdamage option

Add a new boolean option showdamage, if on, outputs a message
like "[HP -2, 14 left]" - several variants have something similar,
but I chose the message based on how eSpeak said it, while keeping
it short.

doc/Guidebook.mn

@@ -4568,6 +4568,9 @@ Control what parts of the score list you are shown at the end (for example
 Only the first letter of each category (\(oqt\(cq, \(oqa\(cq, or \(oqo\(cq)
 is necessary.
 Persistent.
+.lp showdamage
+Whenever your character takes damage, show a message of the damage taken,
+and the amount of hit points left.
 .lp "showexp "
 Show your accumulated experience points on bottom line (default off).
 Persistent.
@@ -5990,6 +5993,8 @@ of moving 8 units at a time.
 Prevent updates to the status lines at the bottom of the screen, if
 your screen-reader reads those lines. The same information can be
 seen via the \(lq#attributes\(rq command.
+.lp showdamage
+Give a message of damage taken and how many hit points are left.
 .hn 2
 Global Configuration for System Administrators
 .pg

doc/Guidebook.tex

@@ -4999,6 +4999,10 @@ Control what parts of the score list you are shown at the end (for example,
 letter of each category (`{\tt t}', `{\tt a}' or `{\tt o}') is necessary.
 Persistent.
 %.lp
+\item[\ib{showdamage}]
+Whenever your character takes damage, show a message of the damage taken,
+and the amount of hit points left.
+%.lp
 \item[\ib{showexp}]
 Show your accumulated experience points on bottom line (default off).
 Persistent.
@@ -6609,6 +6613,9 @@ of moving 8 units at a time.
 Prevent updates to the status lines at the bottom of the screen, if
 your screen-reader reads those lines. The same information can be
 seen via the {\tt \#attributes} command.
+%.lp
+\item[\ib{showdamage}]
+Give a message of damage taken and how many hit points are left.
 \elist
 
 %.hn2

doc/fixes3-7-0.txt

@@ -2493,7 +2493,7 @@ erinyes overhaul; they now attempt to punish heroes who have violated their
 	alignment and get stronger with greater alignment abuse
 accessibility options to tell where on map a message happened (accessiblemsg),
 	to notify when a monster is spotted (spot_monsters), and when
-	a monster moved (mon_movement)
+	a monster moved (mon_movement), when hero takes damage (showdamage)
 if hero is punished or tethered to a buried iron ball and has no inventory (or
 	only carries gold or embedded dragon scales or both), a nymph might
 	remove the chain when finding nothing else to steal