Fix deprecate warning "extern crate ... as ..."

Its arguments were inverted.

Author: seb-m

src/libsyntax/parse/parser.rs

@@ -4780,7 +4780,7 @@ impl<'a> Parser<'a> {
                     self.span_warn(span,
                             format!("this extern crate syntax is deprecated. \
                             Use: extern crate \"{}\" as {};",
-                            the_ident.as_str(), path.ref0().get() ).as_slice()
+                            path.ref0().get(), the_ident.as_str() ).as_slice()
                     );
                     Some(path)
                 } else {None};