Cairo block libs i386/x86_64 fat for OS X, #361

This should resolve #361, the request to provide 32 and 64 bit slices for the cairo block on OS X. My build notes are below in case newer releases are needed at some point, they are re-crafted from the [end to end build for mac os x](http://www.cairographics.org/end_to_end_build_for_mac_os_x/) document.

--

Built on `OS X 10.8.4` with _Command Line Tools_ of `Xcode 4.6.3 (4H1503)`. I was unable to build with the tools provided by `Xcode 5 DP4` or build on `OS X 10.9 DP4`, even with the `Xcode 4.6.3` tools, likely the result of building really old releases.

Grab and untar/gzip `libpng-1.4.3`, `libpixman-0.19.2` and `cairo-1.10.0`. You'll need `pkg-config` as well, I simply installed it via [Homebrew](http://brew.sh/).

```
export BuildDir=/tmp/NILE
mkdir -p ${BuildDir}
```

```
export MACOSX_DEPLOYMENT_TARGET=10.7
export LDFLAGS="-arch i386 -arch x86_64"
export CFLAGS="-Os -arch i386 -arch x86_64"
```

#### libpng
```
cd libpng-1.4.3
./configure --prefix=${BuildDir} --disable-dependency-tracking
make && make install
```

#### pixman
```
cd pixman-0.19.2
./configure --prefix=${BuildDir} --disable-dependency-tracking
make && make install
```

#### cairo
given how old a release we are using,, we need to patch a super old ATSUI API use issue, see [bug 394930](https://bugs.freedesktop.org/show_bug.cgi?id=39493)
```
cd cairo-1.10.0
curl "http://cgit.freedesktop.org/cairo/patch/?id=8664df767cb9dbe48647f9853e3dcf551701d3ca" -o cairo-quartz-font.patch
patch -p1 < cairo-quartz-font.patch
```

```
./configure --prefix=${BuildDir} --disable-dependency-tracking --disable-xlib --without-x  \
pixman_CFLAGS=-I${BuildDir}/include/pixman-1 pixman_LIBS="-L${BuildDir}/lib -lpixman-1" \
png_REQUIRES=libpng png_CFLAGS=-I${BuildDir}/include png_LIBS="-L${BuildDir}/lib -lpng"
make && make install
```