Add PartialEq/Eq impls to proc_macro::{Spacing, Delimiter}

I don't see a reason why those two types shouldn't be tested for equality.

src/libproc_macro/lib.rs

@@ -241,7 +241,7 @@ pub enum TokenNode {
 }
 
 /// Describes how a sequence of token trees is delimited.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[unstable(feature = "proc_macro", issue = "38356")]
 pub enum Delimiter {
     /// `( ... )`
@@ -274,7 +274,7 @@ impl Term {
 }
 
 /// Whether an `Op` is either followed immediately by another `Op` or followed by whitespace.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[unstable(feature = "proc_macro", issue = "38356")]
 pub enum Spacing {
     /// e.g. `+` is `Alone` in `+ =`.