README.MacOS update

[Ben Abbott]

I've pushed a change for README.MacOS

        http://hg.savannah.gnu.org/hgweb/octave/rev/88a8248f5b97

The result can be seen below.

        http://hg.savannah.gnu.org/hgweb/octave/file/88a8248f5b97/README.MacOS

I invite any interested MacOS contributers to review and comment. For changes, 
please attach a changeset or patch.

Those who are not using mercurial, you can create patches by ...

(1) Copy README.MacOS

        $ cp README.MacOS README.MacOS.orig

(2) Edit README.MacOS

(3) Create the patch

        $ diff -u README.MacOS.orig README.MacOS > README.MacOS.patch

Ben