Adding PIL support(with jpeg+png) to kivy-ios

The purpose of this contribution is to add PIL support to the kivy-ios bundle. I modified the tools/build-all.sh script in order to compile PIL(together with libjpeg). This bundle works fine at the moment for my needs. The only issues that I have found are:

1) The Image.save method doesn't work if you write to the filesystem(I also tried writing to the App.get_running_app().user_data_dir directory but it didn't work). However, if you do Image.save(buffer) being buffer a StringIO object and then do f.write(buffer.read()) it will work pretty well.

2) By default, the libraries libjpeg.a and libpil.a are generated in the usual build/lib directory but aren't included in the project generated by tools/create-project.sh by default, you have to add this libraries manually to the project.

I hope thas this patch will help other people to get PIL running on IOS.

Many thanks,

Toni Bagur