message: Update lldb to match clang r331244 (addition of char8_t).
  Also fix misclassification of char16_t and char32_t: these are unsigned types,
  not signed types.
diff: @@ -4914,8 +4914,6 @@ lldb::Encoding ClangASTContext::GetEncoding(lldb::opaque_compiler_type_t type,
  case clang::BuiltinType::Char_S:
  case clang::BuiltinType::SChar:
  case clang::BuiltinType::WChar_S:
  - case clang::BuiltinType::Char16:
  - case clang::BuiltinType::Char32:
  case clang::BuiltinType::Short:
  case clang::BuiltinType::Int:
  case clang::BuiltinType::Long:
  @@ -4926,6 +4924,9 @@ lldb::Encoding ClangASTContext::GetEncoding(lldb::opaque_compiler_type_t type,
  case clang::BuiltinType::Char_U:
  case clang::BuiltinType::UChar:
  case clang::BuiltinType::WChar_U:
  + case clang::BuiltinType::Char8:
  + case clang::BuiltinType::Char16:
  + case clang::BuiltinType::Char32:
  case clang::BuiltinType::UShort:
  case clang::BuiltinType::UInt:
  case clang::BuiltinType::ULong:
  