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

Suggested by G. Brandon Robinson.

man/man1/bundle.1

@@ -7,20 +7,20 @@ bundle \- collect files for distribution
 .SH DESCRIPTION
 .I Bundle
 writes on its standard output a shell script for
-.IM rc (1)
+.MR rc (1)
 or a Bourne shell
 which, when executed,
 will recreate the original
 .IR files .
 Its main use is for distributing small numbers of text files by
-.IM mail (1) .
+.MR mail (1) .
 .PP
 Although less refined than standard archives from
 .I 9ar
 (see
-.IM 9c (1) )
+.MR 9c (1) )
 or
-.IM tar (1) ,
+.MR tar (1) ,
 a
 .IR bundle
 file
@@ -49,7 +49,7 @@ cd gift; sh horse; mk
 (in
 .IR 9c (1)), 
 .IR tar (1), 
-.IM mail (1)
+.MR mail (1)
 .SH BUGS
 .I Bundle
 will not create directories and is unsatisfactory for non-text files.