Rename the rc binary to openrc

Debian requested this rename due to the "rc" binary conflicting with the
"rc" binary from the plan 9 shell.

We also add a deprecation warning to the binary when it is run as rc to
encourage users to switch to openrc instead.

X-Gentoo-Bug: 493958
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=493958

man/rc-service.8

@@ -63,7 +63,7 @@ otherwise -1.
 .Fl r , -resolve
 does the same and also prints the full path of the service to stdout.
 .Sh SEE ALSO
-.Xr rc 8 ,
+.Xr openrc 8 ,
 .Xr stdout 3
 .Sh AUTHORS
 .An Roy Marples <roy@marples.name>