Rename GN public variables.
Rename GN public variables.

direct_dependent_configs => public_configs
Code review: https://webrtc-codereview.appspot.com/22749004/
R=fbarchard


git-svn-id: a51711482b6ba0e1d1ab095578a045eeae45ac9a@1094 16f28f9a-4ce2-e073-06de-1de4eb20be90

rig-project/libyuv,archos-sa/libyuv-avp,granalberto/libyuv,rig-project/libyuv,archos-sa/libyuv-avp,granalberto/libyuv,archos-sa/libyuv-avp,rig-project/libyuv,granalberto/libyuv,granalberto/libyuv