static_footer.txt was removed from skia/docs in r2837, but update-doxygen.sh
requires it to exist in skia-autogen. If skia-autogen is cleared (frequently),
then static_footer.txt can't be found. Add it back to trunk/tools and manually
copy it if needed.
Review URL: https://codereview.appspot.com/6568054
git-svn-id: http://skia.googlecode.com/svn/trunk@5694 2bbb7eff-a529-9590-31e7-b0007b416f81
