Quickinfo and completion entry should display const enum enumName if enum is constant

Handles #1084

tests/cases/fourslash/constEnumQuickInfoAndCompletionList.ts

@@ -0,0 +1,15 @@
+/// <reference path='fourslash.ts' />
+
+////const enum /*1*/e {
+////    a,
+////    b,
+////    c
+////}
+/////*2*/e.a;
+
+goTo.marker('1');
+verify.quickInfoIs("const enum e");
+
+goTo.marker('2');
+verify.completionListContains("e", "const enum e");
+verify.quickInfoIs("const enum e");