update gyp files to build on iOS

Note that there's a hack in SkImageDecoder_CG.cpp --
the necessary defines are included directly. This
is temporary until I can figure out how to include
them properly.
Review URL: https://codereview.appspot.com/6523044

git-svn-id: http://skia.googlecode.com/svn/trunk@5586 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed