Remove macros from the width arguments passed to Bl macros

I've not removed the Er macro from one of the lists in example.9, however,
because it seems to be doing some special kind of magic. Let's leave it
there for now.

share/examples/mdoc/example.1

@@ -47,7 +47,7 @@ It is intended that this example can be used as a template
 when writing a new manual page.
 .Pp
 The options are as follows:
-.Bl -tag -width ".Fl d Ar argument"
+.Bl -tag -width "-d Ar argument"
 .It Fl a
 Example optional
 .Fl a
@@ -76,7 +76,7 @@ command ignores the
 .Ev EXAMPLE
 environment variable.
 .Sh FILES
-.Bl -tag -width ".Pa /dev/null" -compact
+.Bl -tag -width "/dev/null" -compact
 .It Pa /dev/null
 Example of a file in the
 .Sx FILES

share/examples/mdoc/example.3

@@ -57,7 +57,7 @@ and
 The argument
 .Fa mode
 may have one of the following values:
-.Bl -tag -width ".Dv EXAMPLE_ONE"
+.Bl -tag -width "EXAMPLE_ONE"
 .It Dv EXAMPLE_ONE
 First example of a defined variable.
 .Dv EXAMPLE_ONE
@@ -86,7 +86,7 @@ library function ignores the
 .Ev EXAMPLE
 environment variable.
 .Sh FILES
-.Bl -tag -width ".Pa /dev/null" -compact
+.Bl -tag -width "/dev/null" -compact
 .It Pa /dev/null
 Example of a file in the
 .Sx FILES

share/examples/mdoc/example.4

@@ -59,7 +59,7 @@ when writing a new manual page.
 The
 .Nm
 driver supports the following ioctls:
-.Bl -tag -width ".Dv EIOCNULL"
+.Bl -tag -width "EIOCNULL"
 .It Dv EIOCEX
 Example ioctl.
 .It Dv EIOCNULL

share/examples/mdoc/example.9

@@ -54,7 +54,7 @@ and
 The argument
 .Fa mode
 may have one of the following values:
-.Bl -tag -width ".Dv EXAMPLE_ONE"
+.Bl -tag -width "EXAMPLE_ONE"
 .It Dv EXAMPLE_ONE
 First example of a defined variable.
 .Dv EXAMPLE_ONE