Remove references to deprecated extern crate "foo" as bar syntax

This syntax was removed in b24a3b8 but references remained in the
grammar, the reference, rustdoc generation, and some auxiliary test
files that don't seem to have been used since 812637e.

src/doc/grammar.md

@@ -329,7 +329,7 @@ view_item : extern_crate_decl | use_decl ;
 
 ```antlr
 extern_crate_decl : "extern" "crate" crate_name
-crate_name: ident | ( string_lit as ident )
+crate_name: ident | ( ident "as" ident )
 ```
 
 ##### Use declarations

src/doc/reference.md

@@ -752,11 +752,10 @@ provided in the `extern_crate_decl`.
 The external crate is resolved to a specific `soname` at compile time, and a
 runtime linkage requirement to that `soname` is passed to the linker for
 loading at runtime. The `soname` is resolved at compile time by scanning the
-compiler's library path and matching the optional `crateid` provided as a
-string literal against the `crateid` attributes that were declared on the
-external crate when it was compiled. If no `crateid` is provided, a default
-`name` attribute is assumed, equal to the `ident` given in the
-`extern_crate_decl`.
+compiler's library path and matching the optional `crateid` provided against
+the `crateid` attributes that were declared on the external crate when it was
+compiled. If no `crateid` is provided, a default `name` attribute is assumed,
+equal to the `ident` given in the `extern_crate_decl`.
 
 Three examples of `extern crate` declarations:
 

src/librustdoc/html/render.rs

@@ -1643,7 +1643,7 @@ fn item_module(w: &mut fmt::Formatter, cx: &Context,
             clean::ExternCrateItem(ref name, ref src) => {
                 match *src {
                     Some(ref src) => {
-                        try!(write!(w, "<tr><td><code>{}extern crate \"{}\" as {};",
+                        try!(write!(w, "<tr><td><code>{}extern crate {} as {};",
                                     VisSpace(myitem.visibility),
                                     src,
                                     name))