Move CG symbols to CoreFoundation to match Darwin behavior

[Kyle-Ye (Kyle)]

@scanon

You shouldn't be using CGFloat on non-Darwin platforms; its use is necessary to interoperate with a lot of Darwin API, but that's not the case on other platforms, so you should generally be using Float or Double instead in non-Darwin-specific code.

Yes, I could replace CGFloat with Double or Float. But what about CGPoint, CGRect and CGSize? Actually there are a lot of Linux code still use them widely. @scanon

Here is a related post I create years ago CGPoint and CGRect related proposal

And we currently do not have such type in Standard library or Foundation yet. (We do have them in CoreFoundation now on Darwin platform)