Update syn to 0.12 and quote to 0.4

[Eijebong]

No description provided.

[Eijebong]

I didn't rename Data nor VariantData to match syn's new way of naming stuff but I can do that if you want to (this is already a breaking change anyway)

[TedDriggs]

Wow, thank you so much for contributing all this. My goal with Body and VariantData is to match the types exported from syn, so if you don't mind switching them I'll start writing up the release notes.

I'm also going to try aliasing the old names to the new types and see if things work; that would at least give library consumers a chance to get warnings before things break.

[Eijebong]

There, I also added both type aliases you wanted to add