Add server prefix to bumon.xg; avoid rx_call * vs rx_connection * warning

Add server prefix to bumon.xg; avoid rx_call * vs rx_connection * warning

When compiling src/bubasics/bumon.ss.c a warning would be produced
due to an rx_call* being passed into BC_Print which in its client
form requires an rx_connection*.  The server implementation and client
stub each were called BC_Print because there was no server prefix
specified in bumon.xg.  Add prefix 'S' and update bucoord/server.c
to match.

Reviewed-on: http://gerrit.openafs.org/686
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>