Specifying mode in file variables trouble

[Lennart Borgman (gmail)]

I got a question about specifying a multi major mode in a file like this

  <?php // -*- mode: nxhtml-mumamo -*-

This fails with

  Ignoring unknown mode `nxhtml-mumamo-mode'

Could we please compensate for this optimization ... ;-)

In other words: Emacs adds "-mode". That is frustrating, but can of
course not be changed. However if Emacs finds that this fails, can it
then check for just the given "symbol"?

That would allow the example above to work, and it would also help all
users that fail to notice this little twist in the manual. (I know I was
hit by this myself when I tried setting the mode this way.)