* MinGW - skip spec in spec/ruby/optional/capi/thread_spec.rb

C-API Thread function rb_thread_call_without_gvl
      -- runs a C function with the global lock unlocked and unlocks IO with the generic RUBY_UBF_IO

stops/freezes spec tests

See https://bugs.ruby-lang.org/issues/16265

* MinGW - skip test test/resolv/test_dns.rb

Test times out in CI (both AppVeyor & Actions), cannot repo locally

* MinGW - skip test test/ruby/test_thread_queue.rb

* Add Actions mingw.yml

Fixed misspellings reported at [Bug #16437], only in ruby and rubyspec.

This removes the related tests, and puts the related specs behind
version guards.  This affects all code in lib, including some
libraries that may want to support older versions of Ruby.

This removes the security features added by $SAFE = 1, and warns for access
or modification of $SAFE from Ruby-level, as well as warning when calling
all public C functions related to $SAFE.

This modifies some internal functions that took a safe level argument
to no longer take the argument.

rb_require_safe now warns, rb_require_string has been added as a
version that takes a VALUE and does not warn.

One public C function that still takes a safe level argument and that
this doesn't warn for is rb_eval_cmd.  We may want to consider
adding an alternative method that does not take a safe level argument,
and warn for rb_eval_cmd.

Some warnings are because the @o.rb_scan_args call doesn't
include keyword arguments, but the first argument is passed to
rb_scan_args may have a last hash treated as keywords.  Those
should be handled using rb_scan_args_kw on Ruby 2.7.

Other warnings are for the deprecated rb_scan_args behavior to
split option hashes or treat a nil argument as an option hash.
Those warnings should just be suppressed.