Include gif image decoding in images/ on linux.

Build SkImageDecoder_libgif in images project and link against
libgif on linux.

Ensure that the GIF decoder is used in skimage.

Requires a new dependency on libgif-dev when building on linux.

Review URL: https://codereview.chromium.org/14029011

git-svn-id: http://skia.googlecode.com/svn/trunk@8627 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed