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

Almost no change was needed; chunk.h was replaced with buf-t.h.
It dpeends on types/vars.h and types/protocol_buffers.h.
diff --git a/src/acl.c b/src/acl.c
index 16e7753..5b5fd1d 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -22,7 +22,7 @@
 #include <types/global.h>
 
 #include <proto/acl.h>
-#include <proto/arg.h>
+#include <haproxy/arg.h>
 #include <proto/auth.h>
 #include <proto/channel.h>
 #include <proto/log.h>