Print parens on unops when necessary. 'make reformat' output now builds to stage3.

src/comp/front/parser.rs

@@ -1265,6 +1265,7 @@ fn parse_binops(&parser p) -> @ast::expr {
     ret parse_more_binops(p, parse_prefix_expr(p), 0);
 }
 
+const int unop_prec = 100;
 const int as_prec = 5;
 
 fn parse_more_binops(&parser p, @ast::expr lhs, int min_prec)

src/comp/pretty/pprust.rs

@@ -551,7 +551,7 @@ fn print_expr(&ps s, &@ast::expr expr) {
         }
         case (ast::expr_unary(?op,?expr,_)) {
             word(s.s, ast::unop_to_str(op));
-            print_expr(s, expr);
+            print_maybe_parens(s, expr, front::parser::unop_prec);
         }
         case (ast::expr_lit(?lit,_)) {
             print_literal(s, lit);