merge revision(s) ac016394,01fd262e: [Backport #20245]

	Compile code without Symbol GC always

	---
	 symbol.c | 28 +++++++++++++---------------
	 1 file changed, 13 insertions(+), 15 deletions(-)

	Fix crash when checking symbol encoding

	[Bug #20245]

	We sometimes pass in a fake string to sym_check_asciionly. This can crash
	if sym_check_asciionly raises because it creates a CFP with the fake
	string as the receiver which will crash if GC tries to mark the CFP.

	For example, the following script crashes:

	    GC.stress = true
	    Object.const_defined?("\xC3")
	---
	 symbol.c                 | 17 ++++++++++-------
	 test/ruby/test_module.rb |  8 ++++++++
	 2 files changed, 18 insertions(+), 7 deletions(-)