REORG: split "protocols" files into protocol and listener

It was becoming confusing to have protocols and listeners in the same
files, split them.
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index e4aaeed..ed05e02 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -36,8 +36,9 @@
 #include <types/global.h>
 
 #include <proto/fd.h>
+#include <proto/listener.h>
 #include <proto/log.h>
-#include <proto/protocols.h>
+#include <proto/protocol.h>
 #include <proto/proto_uxst.h>
 #include <proto/task.h>