Add clarification to rmr_send_msg manual page

The man page for rm_send_msg() did not emphisize the need for
the user programme to use the returned message pointer for
all future references. This change adds the clarification in
the text of the return value and adds a comment to the example
code.

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I14c21636eafb7b936ad0ba62b3ae621e6f74c50b
1 file changed