doc/Guidebook.mn: Fix table markup nits.

Comment escape sequences inside table entries can wreak havoc.  Use
dummy character instead to visually indicate the deliberate trailing
spaces.  Move the comment explaining why they're there closer to what
they document.  It's okay to have _whole-line_ comments in table data,
because they are on control lines (lines that start with a dot '.').

Also use the dummy character to indicate deliberately empty table cells.

doc/Guidebook.mn

@@ -288,15 +288,15 @@ Dlvl:1 $:993 HP:9(12) Pw:3(3) AC:10 Exp:1/19 T:752 Hungry Conf
 .if t .sp 0.5v
 Figure 1
 .
-.\" Figure 2 uses trailing spaces to force the same width as Figure 1.
 .BR 1
 .ft CR
 .TS
 center box tab(~);
 L.
-Player the Rambler   St:12 Dx:7 Co:18 In:11 Wi:9 Ch:15        \"
+.\" Use trailing spaces to force the same width as Figure 1.
-Neutral $:993 HP:9(12) Pw:3(3) AC:10 Exp:1/19 Hungry          \"
+Player the Rambler   St:12 Dx:7 Co:18 In:11 Wi:9 Ch:15        \&
-Dlvl:1 T:752                                  Conf            \"
+Neutral $:993 HP:9(12) Pw:3(3) AC:10 Exp:1/19 Hungry          \&
+Dlvl:1 T:752                                  Conf            \&
 .TE
 .ft R
 .ce 1
@@ -2828,11 +2828,11 @@ center;
 a n.
 Dragon scale mail	1
 Plate mail, Crystal plate mail	3
-Bronze plate mail, Splint mail,	\"
+Bronze plate mail, Splint mail,	\&
 \ \ \ Banded mail, Dwarvish mithril-coat	4
 Chain mail, Elven mithril-coat	5
 Scale mail, Orcish chain mail	6
-Ring mail, Studded leather armor,	\"
+Ring mail, Studded leather armor,	\&
 \ \ \ Dragon scales	7
 Leather armor, Orcish ring mail	8
 Leather jacket	9