ext/sockets: adding Linux's TCP_USER_TIMEOUT constant.

[lucasnetau]

Useful to ensure PHP sockets are notified of socket failure when Sockets may be closed incorrectly and data can no longer be transmitted. eg Firewall dropping connection or peer device failure (commonly seen with Cloud load balancers).

From tcp(7) :It specifies the maximum amount of time in milliseconds that transmitted data may remain unacknowledged, or buffered data may remain untransmitted (due to zero window size) before TCP will forcibly close the corresponding connection and return ETIMEDOUT to the application.

Following #13816 for PR format for socket constants/

[devnexen]

I see what is happening and why it fails on release 64 bits, the code block is in the wrong place. You just need to move it up in the IPPROTO_TCP section (~line 2082)

[lucasnetau]

I see what is happening and why it fails on release 64 bits, the code block is in the wrong place. You just need to move it up in the IPPROTO_TCP section (~line 2082)

I've moved it up to the IPPROTO_TCP block, I've also followed the setting of the option per the other two options in the IPPROTO_TCP block