bug#12271: 24.1.1: Mac OS X Info-directory-list can not add to first position

[Michael Brand]

Hi all

There is an unexpected behavior with Info-directory-list on Emacs
24.1.1 on Mac OS X: The added path is not placed in the first position.

On Linux, /tmp is in front of Info-directory-list as expected:
/usr/local/bin/emacs-24.1 -Q \
    --eval '(add-to-list (quote Info-default-directory-list) "/tmp")'
C-h v Info-directory-list:
    ("/tmp" "/usr/local/emacs-24.1/share/info/" [...])

On Mac OS X, /tmp is expected in front of Info-directory-list but is not:
/Applications/Emacs-24.1.app/Contents/MacOS/Emacs -Q \
    --eval '(add-to-list (quote Info-default-directory-list) "/tmp")'
C-h v Info-directory-list:
    ("/Applications/Emacs-24.1.app/Contents/Resources/info" "/tmp" [...])

Michael