Converted send_message() to accept a memory buffer rather than the name of

Converted send_message() to accept a memory buffer rather than the name of
a temporary file.  The temporary file is still there, however -- the buffer
read is now done in save_message() instead.  But we're one step closer to
removing the temporary file.  Now we have to convert save_message() (not a
big deal) and all of its callers (somewhat more involved).