Fixes PR 17106 (explicitly typed enums are formatted differently).

Before:
 enum X : int { A, B, C };

After:
 enum X : int {
   A,
   B,
   C
 };

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190054 91177308-0d34-0410-b5e6-96231b3b80d8