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

Suggested by G. Brandon Robinson.

man/man1/rsa.1

@@ -85,7 +85,7 @@ Plan 9 represents DSA and RSA keys as attribute-value pair lists
 prefixed with the string
 .BR key ;
 this is the generic key format used by
-.IM factotum (4) .
+.MR factotum (4) .
 A full DSA private key has the following attributes:
 .TP
 .B proto
@@ -334,9 +334,9 @@ scp auth.keys unix:.ssh/authorized_keys
 .SH SOURCE
 .B \*9/src/cmd/auth
 .SH "SEE ALSO
-.IM factotum (4) ,
-.IM pem (1) ,
-.IM ssh (1)
+.MR factotum (4) ,
+.MR pem (1) ,
+.MR ssh (1)
 .SH BUGS
 There are too many key formats.
 .PP