tmac/tmac.an: define .MR in a groff compatible way

groff 1.23.0 added .MR to its -man macro package.  The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020."  From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.

Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.

Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized.  groff's .MR does not.  This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.

1 files changed, 6 insertions, 6 deletions

diff --git a/man/man1/tweak.1 b/man/man1/tweak.1
index 773ec325..c26992da 100644
--- a/man/man1/tweak.1
+++ b/man/man1/tweak.1
@@ -35,14 +35,14 @@ If the file is a subfont, a second line presents a hexadecimal 16-bit
 .B offset
 to be applied to character values from the subfont
 (typically as stored in a font file; see
-.MR font (7) );
+.MR font 7 );
 and the subfont's
 .BR n ,
 .BR height ,
 and
 .B ascent
 as defined in
-.MR cachechars (3) .
+.MR cachechars 3 .
 .PP
 By means described below, magnified views of portions of the images
 may be displayed.
@@ -61,7 +61,7 @@ default font; the character's
 and
 .BR width
 as defined in
-.MR cachechars (3) ;
+.MR cachechars 3 ;
 and
 .BR iwidth ,
 the physical width of the image in the subfont's image.
@@ -158,9 +158,9 @@ The program will complain once about modified but unwritten files.
 .SH SOURCE
 .B \*9/src/cmd/draw/tweak.c
 .SH "SEE ALSO"
-.MR cachechars (3) ,
-.MR image (7) ,
-.MR font (7)
+.MR cachechars 3 ,
+.MR image 7 ,
+.MR font 7
 .SH BUGS
 For a program written to adjust width tables in fonts,
 .I tweak