Fix bugs in `network_socket_receive_from`.

[hlef]

A few things are wrong with network_socket_receive_from:

• We claim unclaimedBuffer but don't unclaim it on error paths, thus leaking the buffer.
• The check_pointer for port is done on address, likely due to a copy/paste issue.
• The if (received > 0) before setting buffer is redundant as we already checked this a few lines earlier.
• We don't document that the UDP packet will be dropped if an error occurs in this function (timeout, permissions, etc.).
• The documentation of error codes is incomplete.

Address all these issues.