REORG: move applet.h to haproxy/applet{,-t}.h

The type file was slightly tidied. The cli-specific APPCTX_CLI_ST1_* flag
definitions were moved to cli.h. The type file was adjusted to include
buf-t.h and not the huge buf.h. A few call places were fixed because they
did not need this include.
diff --git a/src/ring.c b/src/ring.c
index 0972251..323249d 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -19,10 +19,10 @@
  */
 
 #include <stdlib.h>
+#include <haproxy/applet.h>
 #include <haproxy/api.h>
 #include <haproxy/buf.h>
 #include <haproxy/thread.h>
-#include <types/applet.h>
 #include <proto/cli.h>
 #include <haproxy/ring.h>
 #include <proto/stream_interface.h>