merge revision(s) f96216df,0091fac1,04c704c5,23655e6d,7cb8904a,41168f69,87f6154b: [Backport #17202]

	Remove "All Rights Reserved." from Copyright statement.

	Patch assembly so that it aligns properly

	Removed trailing spaces [ci skip]

	Fix build error on Apple silicon macOS

	This patch will fix following build error on macOS 11.0 + Xcode 12 beta.

	```
	$ ./configure
	$ make V=1
		BASERUBY = /Users/watson/.rbenv/shims/ruby --disable=gems
		CC = clang -fdeclspec
		LD = ld
		LDSHARED = clang -fdeclspec -dynamiclib
		CFLAGS = -O3 -ggdb3 -Wall -Wextra -Werror=deprecated-declarations -Werror=division-by-zero -Werror=implicit-function-declaration -Werror=implicit-int -Werror=misleading-indentation -Werror=pointer-arith -Werror=shorten-64-to-32 -Werror=write-strings -Wmissing-noreturn -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wunused-variable -Werror=extra-tokens -std=gnu99  -pipe
		XCFLAGS = -D_FORTIFY_SOURCE=2 -fstack-protector-strong -fno-strict-overflow -DRUBY_DEVEL=1 -fvisibility=hidden -DRUBY_EXPORT -fPIE -DCANONICALIZATION_FOR_MATHN -I. -I.ext/include/arm64-darwin20 -I./include -I. -I./enc/unicode/12.1.0
		CPPFLAGS = -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT
		DLDFLAGS = -Wl,-undefined,dynamic_lookup -Wl,-multiply_defined,suppress -fstack-protector-strong -Wl,-pie -framework Security -framework Foundation
		SOLIBS = -lpthread -ldl -lobjc
		LANG = ja_JP.UTF-8
		LC_ALL =
		LC_CTYPE =
		MFLAGS =
	Apple clang version 12.0.0 (clang-1200.0.22.19)
	Target: arm64-apple-darwin20.0.0
	Thread model: posix
	InstalledDir: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
	clang -fdeclspec -O3 -ggdb3 -Wall -Wextra -Werror=deprecated-declarations -Werror=division-by-zero -Werror=implicit-function-declaration -Werror=implicit-int -Werror=misleading-indentation -Werror=pointer-arith -Werror=shorten-64-to-32 -Werror=write-strings -Wmissing-noreturn -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wunused-variable -Werror=extra-tokens -std=gnu99  -pipe  -D_FORTIFY_SOURCE=2 -fstack-protector-strong -fno-strict-overflow -DRUBY_DEVEL=1 -fvisibility=hidden -DRUBY_EXPORT -fPIE -DCANONICALIZATION_FOR_MATHN -I. -I.ext/include/arm64-darwin20 -I./include -I. -I./enc/unicode/12.1.0 -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT    -o cont.o -c cont.c
	In file included from cont.c:19:
	./coroutine/ucontext/Context.h:32:5: error: 'getcontext' is deprecated: first deprecated in macOS 10.6 [-Werror,-Wdeprecated-declarations]
	    getcontext(&context->state);
	    ^
	/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/ucontext.h:37:6: note: 'getcontext' has been
	      explicitly marked deprecated here
	int  getcontext(ucontext_t *) __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_5, __MAC_10_6, __IPHONE_2_0, __IPHONE_2_0) __WATCHOS_PROHIBITED __TVOS_PROHIBITED;
	     ^
	In file included from cont.c:19:
	./coroutine/ucontext/Context.h:51:5: error: 'makecontext' is deprecated: first deprecated in macOS 10.6 [-Werror,-Wdeprecated-declarations]
	    makecontext(&context->state, (void(*)(void))coroutine_trampoline, 2, (void*)start, (void*)context);
	    ^
	/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/ucontext.h:38:6: note: 'makecontext' has been
	      explicitly marked deprecated here
	void makecontext(ucontext_t *, void (*)(), int, ...) __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_5, __MAC_10_6, __IPHONE_2_0, __IPHONE_2_0) __WATCHOS_PROHI...
	     ^
	In file included from cont.c:19:
	./coroutine/ucontext/Context.h:59:5: error: 'swapcontext' is deprecated: first deprecated in macOS 10.6 [-Werror,-Wdeprecated-declarations]
	    swapcontext(&current->state, &target->state);
	    ^
	/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/ucontext.h:40:6: note: 'swapcontext' has been
	      explicitly marked deprecated here
	int  swapcontext(ucontext_t * __restrict, const ucontext_t * __restrict) __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_5, __MAC_10_6, __IPHONE_2_0, __IPHONE_...
	     ^
	3 errors generated.
	make: *** [cont.o] Error 1
	```

	Extract correct processor name for ARM64 Macs

	Prefix export symbol prefix to coroutine_transfer

	Revert "Revert "[ruby/fiddle] Use ffi_closure_free by default.
	 (#20)""

	This reverts commit efd641ff.

	This changeset seems to be needed to suppress a warning on Ubuntu 20.04
	https://rubyci.org/logs/rubyci.s3.amazonaws.com/ubuntu/ruby-master/log/20200304T033004Z.log.html.gz
	```
	closure.c:264:5: warning: 'ffi_prep_closure' is deprecated: use ffi_prep_closure_loc instead [-Wdeprecated-declarations]
	  264 |     result = ffi_prep_closure(pcl, cif, callback, (void *)self);
	      |     ^~~~~~
	```

	I guess there was a reason why the commit was reverted (maybe some CIs
	failed?), so try it again.