doc/*.6: Fix macro usage style errors

Fixes:
$ nroff -ww -z -rCHECKSTYLE=4 -man doc/*.[67]
an.tmac:doc/dlb.6:41: style: .IR expects at least 2 arguments, got 1
an.tmac:doc/makedefs.6:125: style: .IR expects at least 2 arguments, got 1
an.tmac:doc/makedefs.6:131: style: .IR expects at least 2 arguments, got 1
an.tmac:doc/makedefs.6:137: style: .IR expects at least 2 arguments, got 1
an.tmac:doc/nethack.6:89: style: .BR expects at least 2 arguments, got 1
an.tmac:doc/nethack.6:129: style: .BR expects at least 2 arguments, got 1
an.tmac:doc/nethack.6:273: style: .BR expects at least 2 arguments, got 1

doc/dlb.6

@@ -38,7 +38,7 @@ dlb \- NetHack data librarian
 }\c
 .RB [ v ]\c
 .B I
-.IR list-file
+.I list-file
 .PP
 .B dlb
 {\c

doc/makedefs.6

@@ -122,19 +122,19 @@ Generate the
 .TP
 .B -1
 Generate the
-.IR epitaph
+.I epitaph
 file.
 .br
 .TP
 .B -2
 Generate the
-.IR engrave
+.I engrave
 file.
 .br
 .TP
 .B -3
 Generate the
-.IR bogusmon
+.I bogusmon
 file.
 .br
 .TP

doc/nethack.6

@@ -86,7 +86,7 @@ Also
 |
 .BR \-R | \-Rog
 |
-.BR \-Ran
+.B \-Ran
 |
 .BR \-S | \-Sam
 |
@@ -126,7 +126,7 @@ Also
 .B \-\-help
 ]
 [
-.BR \-\-showpaths
+.B \-\-showpaths
 ]
 .\" force line wrap now rather than have that happen after the opening brace
 .br
@@ -267,7 +267,7 @@ The
 |
 .BR \-R | \-Rog
 |
-.BR \-Ran
+.B \-Ran
 |
 .BR \-S | \-Sam
 |