Add 'socket' member to 'Native_capability::Dst'

In the final version, the 'socket' will be the only member to remain in
the 'Dst' time. In the transition phase, we store both the old 'tid' and
the 'socket'.

base-linux/include/base/platform_env.h

@@ -327,7 +327,9 @@ namespace Genode {
 				long local_name = _get_env_ulong("parent_local_name");
 
 				/* produce typed capability manually */
-				return reinterpret_cap_cast<Parent>(Native_capability(tid, local_name));
+				typedef Native_capability::Dst Dst;
+				return reinterpret_cap_cast<Parent>(Native_capability(Dst(tid, -1),
+				                                    local_name));
 			}