Use valid `ec` for postponed job.

	Postponed job can be registered from non-Ruby thread, which means
	`ec` in TLS can be NULL. In this case, use main thread's `ec` instead.

	See https://github.com/ruby/ruby/pull/4108
	and https://github.com/ruby/ruby/pull/4336
	---
	 vm_trace.c | 16 ++++++++++++----
	 1 file changed, 12 insertions(+), 4 deletions(-)

	Avoid assert failure when NULL EC is expected

	After 5680c38c75aeb5cbd219aafa8eb48c315f287d97, postponed job APIs now
	expect to be called on native threads not managed by Ruby and handles
	getting a NULL execution context. However, in debug builds the change
	runs into an assertion failure with GET_EC() which asserts that EC is
	non-NULL. Avoid the assertion failure by passing `false` for `expect_ec`
	instead as the intention is to handle when there is no EC.

	Add a test from John Crepezzi and John Hawthorn to exercise this
	situation.

	See GH-4108
	See GH-5094

	[Bug #17573]

	Co-authored-by: John Hawthorn <john@hawthorn.email>
	Co-authored-by: John Crepezzi <john.crepezzi@gmail.com>
	---
	 ext/-test-/postponed_job/postponed_job.c       | 31 ++++++++++++++++++++++++++
	 test/-ext-/postponed_job/test_postponed_job.rb |  7 ++++++
	 vm_trace.c                                     |  2 +-
	 3 files changed, 39 insertions(+), 1 deletion(-)

	Guard array when appending

	This prevents early collection of the array.  The GC doesn't see the
	array on the stack when Ruby is compiled with optimizations enabled

	[ruby-core:105099] [Bug #18140]
	---
	 array.c                 | 1 +
	 test/ruby/test_array.rb | 6 ++++++
	 2 files changed, 7 insertions(+)

	Guard array when appending

	This prevents early collection of the array.  The GC doesn't see the
	array on the stack when Ruby is compiled with optimizations enabled

	Thanks @jhaberman for the test case

	[ruby-core:105099] [Bug #18140]
	---
	 ext/-test-/array/concat/depend          | 321 ++++++++++++++++++++++++++++++++
	 ext/-test-/array/concat/extconf.rb      |   2 +
	 ext/-test-/array/concat/to_ary_conact.c |  64 +++++++
	 test/-ext-/array/test_to_ary_concat.rb  |  20 ++
	 4 files changed, 407 insertions(+)
	 create mode 100644 ext/-test-/array/concat/depend
	 create mode 100644 ext/-test-/array/concat/extconf.rb
	 create mode 100644 ext/-test-/array/concat/to_ary_conact.c
	 create mode 100644 test/-ext-/array/test_to_ary_concat.rb

	Refined test [Bug #18140]

	---
	 ext/-test-/array/concat/to_ary_conact.c | 48 +++++++--------------------------
	 test/ruby/test_array.rb                 |  5 +++-
	 2 files changed, 13 insertions(+), 40 deletions(-)

	Scan the coderange in the given encoding

	---
	 ext/-test-/string/enc_str_buf_cat.c       | 14 ++++++++++++++
	 string.c                                  | 32 ++++++++++++++++++++++---------
	 test/-ext-/string/test_enc_str_buf_cat.rb |  9 +++++++++
	 3 files changed, 46 insertions(+), 9 deletions(-)

	Work around issue transcoding issue with non-ASCII compatible
	 encodings and xml escaping

	When using a non-ASCII compatible source and destination encoding
	and xml escaping (the :xml option to String#encode), the resulting
	string was broken, as it used the correct non-ASCII compatible
	encoding, but contained data that was ASCII-compatible instead of
	compatible with the string's encoding.

	Work around this issue by detecting the case where both the
	source and destination encoding are non-ASCII compatible, and
	transcoding the source string from the non-ASCII compatible
	encoding to UTF-8. The xml escaping code will correctly handle
	the UTF-8 source string and the return the correctly encoded
	and escaped value.

	Fixes [Bug #12052]

	Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
	---
	 test/ruby/test_transcode.rb | 19 +++++++++++++++++++
	 transcode.c                 |  6 ++++++
	 2 files changed, 25 insertions(+)

	=?UTF-8?q?-=20add=20regression=20tests=20for=20U+6E7F=20(?=
	 =?UTF-8?q?=E6=B9=BF)=20in=20ISO-2022-JP?=
	MIME-Version: 1.0
	Content-Type: text/plain; charset=UTF-8
	Content-Transfer-Encoding: 8bit

	  In ISO-2022-JP, the bytes use to code are the same as those for "<>".
	  This adds regression tests to make sure that these bytes, when representing
	  湿, are NOT　escaped with encode("ISO-2022-JP, xml: :text) or similar.
	  These are additional regression tests for #12052.
	---
	 test/ruby/test_transcode.rb | 3 +++
	 1 file changed, 3 insertions(+)

	rb_enc_interned_str: handle autoloaded encodings

	If called with an autoloaded encoding that was not yet
	initialized, `rb_enc_interned_str` would crash with
	a NULL pointer exception.

	See: https://github.com/ruby/ruby/pull/4119#issuecomment-800189841
	---
	 encoding.c                        | 28 ++++++++++++----------------
	 ext/-test-/string/depend          |  3 +++
	 ext/-test-/string/fstring.c       | 15 +++++++++++++++
	 internal/encoding.h               |  3 +++
	 string.c                          |  4 ++++
	 test/-ext-/string/test_fstring.rb | 16 ++++++++++++++++
	 6 files changed, 53 insertions(+), 16 deletions(-)