BUILD: stream-int: fix a few includes dependencies

The stream-int code doesn't need to load server.h as it doesn't use
servers at all. However removing this one reveals that proxy.h was
lacking types/checks.h that used to be silently inherited from
types/server.h loaded before in stream_interface.h.

include/proto/stream_interface.h

@@ -25,7 +25,6 @@
 #include <stdlib.h>
 
 #include <common/config.h>
-#include <types/server.h>
 #include <types/stream.h>
 #include <types/stream_interface.h>
 #include <proto/applet.h>

include/types/proxy.h

@@ -40,6 +40,7 @@
 
 #include <types/acl.h>
 #include <types/backend.h>
+#include <types/checks.h>
 #include <types/counters.h>
 #include <types/filters.h>
 #include <types/freq_ctr.h>