Dear All,

 Please find attached a patch (against master) which takes care of the
following issue. Assume I have a block like this

#+begin_src sh :tangle no
  This should not be tangled
#+end_src

Then the block is correctly ignored when tangling the whole file, but
erroneously tangled (to a file named "no") when tangling is run with the
universal argument (so that only the current block should be tangled)

This happens because the check for the "no" option is not performed when
tangling a single block.  In the proposed patch I address this issue by
checking for the "no" option in the function org-babel-effective-tangled-
filename