Add configurable symbol entry for strange object

dat/symbols

@@ -513,6 +513,7 @@ start: Blank
         S_ss4: \032
         S_statue_trap: \032
         S_stone: \032
+        S_strange_obj: \032
         S_sw_bc: \032
         S_sw_bl: \032
         S_sw_br: \032

doc/Guidebook.mn

@@ -3285,6 +3285,7 @@ s	S_spider	(arachnid or centipede)
 *	S_ss4	(magic shield 4 of 4)
 ^	S_statue_trap	(statue trap)
 	S_stone	(dark part of a room)
+]	S_strange_obj	(strange object)
 -	S_sw_bc	(swallow bottom center)
 `\e'	S_sw_bl	(swallow bottom left)
 /	S_sw_br	(swallow bottom right)

doc/Guidebook.tex

@@ -3926,6 +3926,7 @@ Default  & Symbol Name                & Description\\
 \verb@*@ & S\verb+_+ss4                     &	(magic shield 4 of 4)\\
 \verb@^@ & S\verb+_+statue\verb+_+trap            &	(statue trap)\\
 \verb@ @ & S\verb+_+stone                   &	(dark part of a room)\\
+\verb@]@ & S\verb+_+strange\verb+_+obj      &	(strange object)\\
 \verb@-@ & S\verb+_+sw\verb+_+bc                  &	(swallow bottom center)\\
 \verb@\@ & S\verb+_+sw\verb+_+bl                  &	(swallow bottom left)\\
 \verb@/@ & S\verb+_+sw\verb+_+br                  &	(swallow bottom right	)\\

src/drawing.c

@@ -671,6 +671,7 @@ struct symparse loadsyms[] = {
     { SYM_PCHAR, S_explode7, "S_explode7" },
     { SYM_PCHAR, S_explode8, "S_explode8" },
     { SYM_PCHAR, S_explode9, "S_explode9" },
+    { SYM_OC, ILLOBJ_CLASS + SYM_OFF_O, "S_strange_obj" },
     { SYM_OC, WEAPON_CLASS + SYM_OFF_O, "S_weapon" },
     { SYM_OC, ARMOR_CLASS + SYM_OFF_O, "S_armor" },
     { SYM_OC, ARMOR_CLASS + SYM_OFF_O, "S_armour" },