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/stats.c b/src/stats.c
index 0bb7481..b527eaf 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -24,6 +24,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
+#include <haproxy/applet-t.h>
 #include <haproxy/api.h>
 #include <common/cfgparse.h>
 #include <haproxy/check.h>
@@ -49,7 +50,6 @@
 #include <haproxy/version.h>
 #include <haproxy/base64.h>
 
-#include <types/applet.h>
 #include <types/cli.h>
 #include <types/stats.h>