[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:

https://github.com/thecodingmachine/safe/blob/3a6e43b4be3d3d65b272c2660300a50658ce168b/generated/exec.php#L95-L102