Remove Nonterminal::NtTT.

It's only needed for macro expansion, not as a general element in the
AST. This commit removes it, adds `NtOrTt` for the parser and macro
expansion cases, and renames the variants in `NamedMatch` to better
match the new type.

compiler/rustc_parse/src/parser/mod.rs

@@ -19,7 +19,7 @@ pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
 pub use path::PathStyle;
 
 use rustc_ast::ptr::P;
-use rustc_ast::token::{self, DelimToken, Token, TokenKind};
+use rustc_ast::token::{self, DelimToken, Nonterminal, Token, TokenKind};
 use rustc_ast::tokenstream::AttributesData;
 use rustc_ast::tokenstream::{self, DelimSpan, Spacing};
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
@@ -1507,3 +1507,9 @@ pub enum FlatToken {
     /// handling of replace ranges.
     Empty,
 }
+
+#[derive(Debug)]
+pub enum NtOrTt {
+    Nt(Nonterminal),
+    Tt(TokenTree),
+}