Fetch libexif 0.6.21 to include the security fixes.

BUG=none
TEST=none
Review URL: https://chromiumcodereview.appspot.com/10792004

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/libexif@146817 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
11 files changed
tree: 1b3cadc532b39070079af20c832cd8d30c649273
  1. sources/