tmac: rename IM (italic manual) to MR (manual reference)

Suggested by G. Brandon Robinson.

man/man1/paint.1

@@ -19,7 +19,7 @@ If the optional
 argument is specified, then it is read and used as the canvas.
 .I Paint
 only recognizes Plan 9 bitmap format (see
-.IM image (6) ).
+.MR image (6) ).
 .PP
 A number of immediate keyboard commands are recognized:
 .TP
@@ -74,12 +74,12 @@ Quits the program.
 .SH SOURCE
 .B /sys/src/cmd/paint.c
 .SH "SEE ALSO"
-.IM resample (1) ,
-.IM rotate (1) ,
-.IM crop (1) ,
-.IM jpg (1) ,
-.IM page (1) ,
-.IM image (6)
+.MR resample (1) ,
+.MR rotate (1) ,
+.MR crop (1) ,
+.MR jpg (1) ,
+.MR page (1) ,
+.MR image (6)
 .SH HISTORY
 .I Paint
 first appeared in 9front (October, 2011).