revert function name to ess-mpi-handle-messages

as requested by @vspinu, but for now, leave the mpi delimiter variables names
double-dashed as explicitly requested by @lionel-

Author: dankessler

lisp/ess-tracebug.el

@@ -1227,7 +1227,7 @@ value from EXPR and then sent to the subprocess."
    ((string= el "t") t)
    (t el)))
 
-(defun ess--mpi-handle-messages (buf)
+(defun ess-mpi-handle-messages (buf)
   "Handle all mpi messages in BUF and delete them.
 The MPI message has the form \001TYPE\002FIELD...\003 where TYPE
 is the type of the messages on which handlers in