[patch 0/1][RFC] add a private field to the sock structure

When a socket is created it is sometime useful to store a specific information
for this socket.
 
This information can be for examples: 
	* a creation time
	* a pid
	* a uid/gid
	* a container identifier
	* a pointer to a more specific structure
	* ...

The following patch is a proposition to add a private anonymous pointer
field to the common part of the sock structure.

--