rustc: Obsolete the @ syntax entirely

This removes all remnants of `@` pointers from rustc. Additionally, this removes
the `GC` structure from the prelude as it seems odd exporting an experimental
type in the prelude by default.

Closes #14193
[breaking-change]

src/libsyntax/ext/asm.rs

@@ -20,6 +20,8 @@ use parse;
 use parse::token::InternedString;
 use parse::token;
 
+use std::gc::GC;
+
 enum State {
     Asm,
     Outputs,

src/libsyntax/ext/base.rs

@@ -20,7 +20,7 @@ use parse::token::{InternedString, intern, str_to_ident};
 use util::small_vector::SmallVector;
 
 use std::collections::HashMap;
-use std::gc::Gc;
+use std::gc::{Gc, GC};
 
 // new-style macro! tt code:
 //

src/libsyntax/ext/build.rs

@@ -21,7 +21,7 @@ use parse::token::special_idents;
 use parse::token::InternedString;
 use parse::token;
 
-use std::gc::Gc;
+use std::gc::{Gc, GC};
 
 // Transitional reexports so qquote can find the paths it is looking for
 mod syntax {

src/libsyntax/ext/concat_idents.rs

@@ -16,7 +16,7 @@ use owned_slice::OwnedSlice;
 use parse::token;
 use parse::token::{str_to_ident};
 
-use std::string::String;
+use std::gc::GC;
 
 pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
                          -> Box<base::MacResult> {

src/libsyntax/ext/deriving/generic/mod.rs

@@ -178,7 +178,7 @@ StaticEnum(<ast::EnumDef of C>, ~[(<ident of C0>, <span of C0>, Unnamed(~[<span
 */
 
 use std::cell::RefCell;
-use std::gc::Gc;
+use std::gc::{Gc, GC};
 
 use ast;
 use ast::{P, EnumDef, Expr, Ident, Generics, StructDef};

src/libsyntax/ext/expand.rs

@@ -29,7 +29,7 @@ use visit;
 use visit::Visitor;
 use util::small_vector::SmallVector;
 
-use std::gc::Gc;
+use std::gc::{Gc, GC};
 
 pub fn expand_expr(e: Gc<ast::Expr>, fld: &mut MacroExpander) -> Gc<ast::Expr> {
     match e.node {
@@ -1030,6 +1030,8 @@ mod test {
     use visit;
     use visit::Visitor;
 
+    use std::gc::GC;
+
     // a visitor that extracts the paths
     // from a given thingy and puts them in a mutable
     // array (passed in to the traversal)

src/libsyntax/ext/format.rs

@@ -20,7 +20,7 @@ use rsparse = parse;
 
 use parse = fmt_macros;
 use std::collections::HashMap;
-use std::gc::Gc;
+use std::gc::{Gc, GC};
 
 #[deriving(PartialEq)]
 enum ArgumentType {

src/libsyntax/ext/tt/macro_parser.rs

@@ -22,6 +22,7 @@ use parse::token::{Token, EOF, Nonterminal};
 use parse::token;
 
 use std::rc::Rc;
+use std::gc::GC;
 use std::collections::HashMap;
 
 /* This is an Earley-like parser, without support for in-grammar nonterminals,