Auto merge of #34829 - cgswords:tstream, r=nrc

Added tokenstream parser procedure

A tiny PR that simply adds a procedure for parsing `TokenStream`s to the parser in `src/libsyntax`. This is to ease using `TokenStream`s with the current (old) procedural macro system.

src/libsyntax/parse/mod.rs

@@ -228,10 +228,18 @@ pub fn filemap_to_parser<'a>(sess: &'a ParseSess,
 // compiler expands into it
 pub fn new_parser_from_tts<'a>(sess: &'a ParseSess,
                                cfg: ast::CrateConfig,
-                               tts: Vec<tokenstream::TokenTree>) -> Parser<'a> {
+                               tts: Vec<tokenstream::TokenTree>)
+                               -> Parser<'a> {
     tts_to_parser(sess, tts, cfg)
 }
 
+pub fn new_parser_from_ts<'a>(sess: &'a ParseSess,
+                              cfg: ast::CrateConfig,
+                              ts: tokenstream::TokenStream)
+                              -> Parser<'a> {
+    tts_to_parser(sess, ts.tts, cfg)
+}
+
 
 // base abstractions