REORG: applet: move the applet definitions out of stream_interface

We're tidying the definitions so that appctx lives on its own. A new
set of applet.h files has been added for this purpose.
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 4375bec..d416ad0 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -37,6 +37,7 @@
 #include <common/version.h>
 #include <common/base64.h>
 
+#include <types/applet.h>
 #include <types/global.h>
 
 #include <proto/backend.h>