mac: enable-retina is now the default

Change-Id: I311d6b359007b1d5799673e3d7733bdf2177df88
configure: kill unsupported mac SDK

Change-Id: I1185539ecee1b9ede161bffcea9c13af0ade9510
mac: clean-up obsolete conditional code based on old SDK

Change-Id: Ie2d476780a48b5815961598e214343d5def962c1