Use a non-ambiguous character for encoding bare functions

I was using 'R' and that was already used for records.

Issue #1022

Author: brson

src/comp/metadata/tydecode.rs

@@ -245,6 +245,11 @@ fn parse_ty(st: @pstate, sd: str_def) -> ty::t {
         ret ty::mk_fn(st.tcx, ast::proto_fn, func.args, func.ty, func.cf,
                       func.cs);
       }
+      'f' {
+        let func = parse_ty_fn(st, sd);
+        ret ty::mk_fn(st.tcx, ast::proto_fn, func.args, func.ty, func.cf,
+                      func.cs);
+      }
       'W' {
         let func = parse_ty_fn(st, sd);
         ret ty::mk_fn(st.tcx, ast::proto_iter, func.args, func.ty, func.cf,

src/comp/metadata/tyencode.rs

@@ -197,7 +197,7 @@ fn enc_proto(w: io::writer, proto: proto) {
       proto_iter. { w.write_char('W'); }
       proto_fn. { w.write_char('F'); }
       proto_block. { w.write_char('B'); }
-      proto_bare. { w.write_char('R'); }
+      proto_bare. { w.write_char('f'); }
     }
 }