imageio_util: s/ExUtil/ImgIoUtil/

ExUtil(SetBinaryMode|ReadFile|ReadFromStdin|WriteFile|CopyPlane) ->
ImgIoUtil(SetBinaryMode|ReadFile|ReadFromStdin|WriteFile|CopyPlane)

Change-Id: I5497f8fe514347efeb83b8b8866ef334390fc18e
12 files changed