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/cli.c b/src/cli.c
index 186aad4..e3b914d 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -26,6 +26,7 @@
 
 #include <net/if.h>
 
+#include <haproxy/applet-t.h>
 #include <haproxy/api.h>
 #include <common/cfgparse.h>
 #include <haproxy/check.h>
@@ -45,7 +46,6 @@
 #include <haproxy/version.h>
 #include <haproxy/base64.h>
 
-#include <types/applet.h>
 #include <haproxy/global.h>
 #include <types/stats.h>