MEDIUM: peers: don't rely on conn->xprt_ctx anymore

We make the peers code use applet->ptr instead of conn->xprt_ctx to
store the pointer to the current peer. That way it does not depend
on a connection anymore.
diff --git a/include/types/stream_interface.h b/include/types/stream_interface.h
index 5ce65a6..6748fbf 100644
--- a/include/types/stream_interface.h
+++ b/include/types/stream_interface.h
@@ -120,6 +120,7 @@
 		unsigned int st0;     /* CLI state for stats, session state for peers */
 		unsigned int st1;     /* prompt for stats, session error for peers */
 		unsigned int st2;     /* output state for stats, unused by peers  */
+		void *ptr;            /* struct peer for peers */
 
 		union {
 			struct {