for threaded context, it solely uses a new api only available on
illumos.
Here using a common older api to get the stack info for the current
thread.
while at it, completing stack_limit_010 test for these platforms.
Stack overflows can be detected as long as C stack frames between two
execute_ex() calls use less than zend.reserved_stack_size bytes of stack.
The default value of zend.reserved_stack_size accounts for the largest stack
users, but MSAN instrumentation increases usage considerably: php_pcre2_match
uses more than 200KiB of stack in some MSAN build, compared to 20KiB without MSAN
according to -fstack-usage.
