Add missing symbols to Blank symset and Guidebook

dat/symbols

@@ -453,11 +453,13 @@ start: Blank
         S_hbeam: \032
         S_hcdbridge: \032
         S_hcdoor: \032
+        S_hodbridge: \032
         S_hodoor: \032
         S_hole: \032
         S_human: \032
         S_humanoid: \032
         S_hwall: \032
+        S_ice: \032
         S_imp: \032
         S_invisible: \032
         S_jabberwock: \032
@@ -543,7 +545,9 @@ start: Blank
         S_vbeam: \032
         S_vcdbridge: \032
         S_vcdoor: \032
+        S_venom: \032
         S_vibrating_square: \032
+        S_vodbridge: \032
         S_vodoor: \032
         S_vortex: \032
         S_vwall: \032

doc/Guidebook.mn

@@ -3543,6 +3543,7 @@ h	S_humanoid	(humanoid)
 -	S_hwall	(horizontal wall)
 .	S_ice	(ice)
 i	S_imp	(imp or minor demon)
+I	S_invisible	(invisible monster)
 J	S_jabberwock	(jabberwock)
 j	S_jelly	(jelly)
 k	S_kobold	(kobold)

doc/Guidebook.tex

@@ -4334,6 +4334,7 @@ Default  & Symbol Name                & Description\\
 \verb@-@ & S\verb+_+hwall                   &	(horizontal wall)\\
 \verb@.@ & S\verb+_+ice                     &	(ice)\\
 \verb@i@ & S\verb+_+imp                     &	(imp or minor demon)\\
+\verb@I@ & S\verb+_+invisible               &	(invisible monster)\\
 \verb@J@ & S\verb+_+jabberwock              &	(jabberwock)\\
 \verb@j@ & S\verb+_+jelly                   &	(jelly)\\
 \verb@k@ & S\verb+_+kobold                  &	(kobold)\\