protocols, messages, cords, oh my!

[Erik Ostrom <eostrom@research.att.com>]

yet another alternative, btw, is to use a special character to
indicate the separation between protocol name and message/cord name.
for example,

  mcp-cord:open
  mcp-cord:msg
  mcp-cord:close

  whiteboard:main

This would ease parsing and allow us to eliminate restrictions on the
number of words in a message.

Using a colon as the separator in a cord type conflicts with the
current lexical distinction between keywords and unquoted values.  Of
course we could use a different separator; or, we could rewrite the
lexical distinction so that colons are acceptable in an unquoted value
so long as they are not located at its _end_.  Of course, then we'd
also have to go without 'null' cord names.  Finally, we could just use
colons and quote them.  I just think colons look nice.

--Erik