derive: update dependencies

[hcpl]

Fixes #352.

Newer versions support new syntax, such as pub(restricted).

[cuviper]

warning: unreachable expression
  --> derive/tests/trivial.rs:15:43
   |
15 | #[derive(Debug, PartialEq, FromPrimitive, ToPrimitive)]
   |                                           ^^^^^^^^^^^
   |
   = note: #[warn(unreachable_code)] on by default

error[E0004]: non-exhaustive patterns: type Color is non-empty
  --> derive/tests/trivial.rs:15:43
   |
15 | #[derive(Debug, PartialEq, FromPrimitive, ToPrimitive)]
   |                                           ^^^^^^^^^^^
   |

help: Please ensure that all possible cases are being handled; possibly adding wildcards or more match arms.
  --> derive/tests/trivial.rs:15:43
   |
15 | #[derive(Debug, PartialEq, FromPrimitive, ToPrimitive)]
   |                                           ^^^^^^^^^^^

error: aborting due to previous error

error: Could not compile `num-derive`.

[cuviper]

Looks like those errors are just because #(variants,)* should now be #(#variants,)*.

[cuviper]

Can we support the full ConstExpr, instead of picking it apart? This will fail on even simple values like -100 which will map to something like Unary(Neg, Lit(Int(100))). Nevermind more complicated expressions. (It seems the old syn just failed to parse it at all.)

I'm thinking instead of idx, we store the actual expr and an offset 0, which we encode as quote!(... #expr + #offset ...). If the next variant has a discriminant, update expr and set offset back to 0, otherwise reuse the former expr with an incremented offset.

[cuviper]

Please do move this to the new repo and issue, rust-num/num-derive#2