Update pretty printer to print out disr. values.

Partly fixes issue #1510.  "rustc --pretty=typed" fails.

src/comp/syntax/print/pprust.rs

@@ -428,6 +428,14 @@ fn print_item(s: ps, &&item: @ast::item) {
                     commasep(s, consistent, v.node.args, print_variant_arg);
                     pclose(s);
                 }
+                alt v.node.disr_expr {
+                  some(expr) {
+                    nbsp(s);
+                    word_nbsp(s, "=");
+                    print_expr(s, expr);
+                  }
+                  _ {}
+                }
                 word(s.s, ";");
                 maybe_print_trailing_comment(s, v.span, none::<uint>);
             }

src/test/run-pass/enum-disr-val-pretty.rs

@@ -0,0 +1,16 @@
+// pp-exact
+
+enum color { red = 1; green; blue; imaginary = -1; }
+
+fn main() {
+    test_color(red, 1, "red");
+    test_color(green, 2, "green");
+    test_color(blue, 3, "blue");
+    test_color(imaginary, -1, "imaginary");
+}
+
+fn test_color(color: color, val: int, name: str) unsafe{
+    assert (color as int == val);
+    assert (color as float == val as float);
+}
+