CLEANUP: include: tree-wide alphabetical sort of include files

This patch fixes all the leftovers from the include cleanup campaign. There
were not that many (~400 entries in ~150 files) but it was definitely worth
doing it as it revealed a few duplicates.
diff --git a/include/haproxy/backend.h b/include/haproxy/backend.h
index a5e3b46..f6b25e7 100644
--- a/include/haproxy/backend.h
+++ b/include/haproxy/backend.h
@@ -22,8 +22,8 @@
 #ifndef _HAPROXY_BACKEND_H
 #define _HAPROXY_BACKEND_H
 
-#include <haproxy/backend-t.h>
 #include <haproxy/api.h>
+#include <haproxy/backend-t.h>
 #include <haproxy/proxy-t.h>
 #include <haproxy/server-t.h>
 #include <haproxy/stream-t.h>