global tick API support

[shiguangqi]

Adding this API so we can set a global default ticks number that can be used in every php file, avoiding set declare(ticks=N) at the beginning of each file many times.
Please considering this request, it is so important to us, we have used tick to implemented preemptive scheduling for Swoole Coroutine, it is bad to set declare(ticks=N) in each php file. we can use zend_set_global_tick API in our extension by once with a default value.

[shiguangqi]

I am one of developers of Swoole(https://github.com/swoole/swoole-src) from china, with the request we can implement following, including involves many php files.
php -dswoole.ticks=1000 test.php

<?php
$max_msec = 10;
Co::set(['max_exec_msec' => $max_msec]);

$start = microtime(true);
echo "start\n";
$flag = 1;

go(function () use (&$flag, $max_msec) {
    echo "coro 1 start to loop\n";
    $i = 0;
    while ($flag) {
        $i++;
    }
    echo "coro 1 can exit\n";
});

$end = microtime(true);
$msec = ($end - $start) * 1000;

go(function () use (&$flag) {
    echo "coro 2 set flag = false\n";
    $flag = false;
});
echo "end\n";
?>
--EXPECTF--
start
coro 1 start to loop
coro 2 set flag = false
end
coro 1 can exit

[KalleZ]

This patch has uses spaces instead of tabs, please fix that.

The function body is missing ZEND_API.

The new CG(ticks) should be initialized before use.

[shiguangqi]

Thank you so much for your reply, I have modified the request as your help, please help review again.

[shiguangqi]

I have updated the request just now and using a static zend_default_ticks instead of CG(ticks), cause CG(ticks) will cause ABI incompatible. Please help review again, Thank you so much!

[cmb69]

Using a global variable would not be thread-safe, would it? An ABI incompatibility due to introducing CG(ticks) in PHP 8 (or even 7.4) would be permissible.

[shiguangqi]

@cmb69 I think it is thread-safe, only call zend_set_global_tick on MINIT phase before compile PHP file will be useful. once we set zend_default_ticks value, it would not be modified again. the default value will be effective in all scope except the file using declare(ticks=N) individual.