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

Nothing fancy, includes were already OK. The proto didn't reference the
type, this was fixed. Still references proxy.h and server.h from types/.
diff --git a/src/backend.c b/src/backend.c
index 8fe0038..acb80fa 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -26,6 +26,7 @@
 #include <haproxy/http_htx.h>
 #include <haproxy/htx.h>
 #include <haproxy/lb_chash.h>
+#include <haproxy/lb_fas.h>
 #include <haproxy/obj_type.h>
 #include <haproxy/ticks.h>
 #include <haproxy/time.h>
@@ -38,7 +39,6 @@
 #include <proto/backend.h>
 #include <proto/channel.h>
 #include <proto/checks.h>
-#include <proto/lb_fas.h>
 #include <proto/lb_fwlc.h>
 #include <proto/lb_fwrr.h>
 #include <proto/lb_map.h>