[Feature request] Add support for proc_*

[JoniJnm]

Could be a good idea?

• proc_open returns false on error
• proc_close returns -1 on error

Note: proc_nice exists:

safe/generated/exec.php

Lines 95 to 102 in 3a6e43b

	function proc_nice(int $priority): void
	{
	error_clear_last();
	$safeResult = \proc_nice($priority);
	if ($safeResult === false) {
	throw ExecException::createFromPhpError();
	}
	}

[shish]

proc_open is added -- proc_close seems like the return code depends on compilation flags and is generally unreliable, and even in ideal conditions I can't figure out how to make it return an error, so I'll not add that for now. If somebody can come up with a unit test which demonstrates what is necessary to make proc_close return -1, then we can add it :)