Fix uninitialized values and bad enum conversions found by UBSAN.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@237738 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/type_traits/convert_to_integral.pass.cpp

@@ -57,7 +57,7 @@ void check_enum_types()
 }
 
 
-enum enum1 {};
+enum enum1 { zero = 0, one = 1 };
 enum enum2 {
   value = std::numeric_limits<unsigned long>::max()
 };