Fix lion libpng

lion-libpng

Fixing Lion libpng issues
-------------------------

Until this issue https://github.com/mxcl/homebrew/issues/4468 is resolved installing Lion screws up ImageMagick's png support.  The following steps are a hacky work around to get things going again. `identify: memory allocation failed` is the error message you'll receive before applying the fix.

    brew uninstall imagemagick
    cd /usr/X11R6/lib
    sudo mv libpng.dylib libpng.old.dylib
    sudo ln -s libpng12.0.dylib libpng.dylib
    brew install imagemagick