Enhance -Wtautological-constant-out-of-range-compare to include the name of the enum constant.

This is QoI.  Fixes <rdar://problem/13076064>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177190 91177308-0d34-0410-b5e6-96231b3b80d8