(old)
test.rb:4: warning: The last argument is used as the keyword parameter
test.rb:1: warning: for `foo' defined here; maybe ** should be added to the call?

(new)
test.rb:4: warning: The last argument is used as keyword parameters; maybe ** should be added to the call
test.rb:1: warning: The called method `foo' is defined here

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

... like we do so for struct timeval at several hundreds of lines above.
Depending on OS/Compiler, this can be the first place for the struct to
appear.  To make sure the struct is global, we need a forward
declaration at this point.

rb_eval_cmd takes a safe level, and now that $SAFE is deprecated,
it should be deprecated as well.

Replace with rb_eval_cmd_kw, which takes a keyword flag.  Switch
the two callers to this function.

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.

These functions are the same, so remove one.

Co-authored-by: John Hawthorn <john@hawthorn.email>

Apply __attribute__((__returns_nonnull__)) when available.

clang also supports __attribute__((__alloc_size__)) so why not use
it when the compiler says it does.