merge revision(s) 2bc293e8,d0e6c6e6,cc0dc67b,e1eff837,0ab0b86c,6911b4bc: [Backport #17854]

	cdhash_cmp: can take rational literals

	Rational literals are those integers suffixed with `r`.  They tend to
	be a part of more complex expressions like `123/456r`, but in theory
	they can live alone.  When such "bare" rational literals are passed to
	case-when branch, we have to take care of them.  Fixes [Bug #17854]
	---
	 common.mk                  |  1 +
	 compile.c                  |  7 +++++++
	 internal/rational.h        |  1 +
	 rational.c                 | 13 ++++++++++---
	 test/ruby/test_rational.rb |  7 +++++++
	 5 files changed, 26 insertions(+), 3 deletions(-)

	cdhash_cmp: rational literals with fractions

	Nobu kindly pointed out that rational literals can have fractions.
	---
	 compile.c                  | 5 +++--
	 test/ruby/test_rational.rb | 4 ++++
	 2 files changed, 7 insertions(+), 2 deletions(-)

	cdhash_cmp: can also take complex

	There are complex literals `123i`, which can also be a case condition.
	---
	 compile.c                  | 15 +++++++++++----
	 complex.c                  | 12 +++++++++---
	 internal/complex.h         |  1 +
	 test/ruby/test_rational.rb |  4 ++++
	 4 files changed, 25 insertions(+), 7 deletions(-)

	cdhash_cmp: recursively apply

	For instance a rational's numerator can be a bignum.  Comparison using
	C's == can be insufficient.
	---
	 compile.c | 4 ++--
	 1 file changed, 2 insertions(+), 2 deletions(-)

	cdhash_cmp: should use ||

	cf: https://github.com/ruby/ruby/pull/4469#discussion_r628386707
	---
	 compile.c | 4 ++--
	 1 file changed, 2 insertions(+), 2 deletions(-)

	test_cdhash: refactor change class

	It is now strange to test Complex in a class named Rational_Test.
	---
	 test/ruby/test_rational.rb | 15 ---------------
	 test/ruby/test_syntax.rb   | 15 +++++++++++++++
	 2 files changed, 15 insertions(+), 15 deletions(-)