Add pid as an option to UCred struct
Add pid as an option to UCred struct

Currently, PID will be populated for Linux, and set to None for BSDs.

aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust