Cut out a bunch of Result and panictry! boilerplate from libsyntax.

[breaking-change] if you use any of the changed functions, you'll need to remove a try! or panictry!

src/libsyntax/parse/mod.rs

@@ -261,7 +261,7 @@ pub fn tts_to_parser<'a>(sess: &'a ParseSess,
                          cfg: ast::CrateConfig) -> Parser<'a> {
     let trdr = lexer::new_tt_reader(&sess.span_diagnostic, None, None, tts);
     let mut p = Parser::new(sess, cfg, Box::new(trdr));
-    panictry!(p.check_unknown_macro_variable());
+    p.check_unknown_macro_variable();
     p
 }