Implement NameError::message#clone for Ractor

	---
	 bootstraptest/test_ractor.rb   | 13 +++++++++++++
	 error.c                        | 35 +++++++++++++++++++++++++++++++++--
	 test/objspace/test_objspace.rb |  9 +++++++++
	 3 files changed, 55 insertions(+), 2 deletions(-)