Replace 'default' in an enum-over-a-switch with the missing list.

This suppressed the Wswitch warning causing me to miss it and write an
assertion failure.

llvm-svn: 362245
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index e8f559a..8f3ebc2 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -429,7 +429,11 @@
   case EST_NoThrow:
     OS <<"__attribute__((nothrow))";
     break;
-  default:
+  case EST_None:
+  case EST_MSAny:
+  case EST_Unevaluated:
+  case EST_Uninstantiated:
+  case EST_Unparsed:
     llvm_unreachable("This spec type is compatible with none.");
   }