REORG: include: move frontend.h to haproxy/frontend.h

There was no type file for this one, it only contains frontend_accept().
diff --git a/src/stream.c b/src/stream.c
index 4bd8d51..57a0d91 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -21,6 +21,7 @@
 #include <haproxy/dict.h>
 #include <haproxy/dns.h>
 #include <haproxy/dynbuf.h>
+#include <haproxy/frontend.h>
 #include <haproxy/hlua.h>
 #include <haproxy/istbuf.h>
 #include <haproxy/thread.h>
@@ -45,7 +46,6 @@
 #include <haproxy/fd.h>
 #include <proto/filters.h>
 #include <haproxy/freq_ctr.h>
-#include <proto/frontend.h>
 #include <proto/http_rules.h>
 #include <proto/listener.h>
 #include <proto/log.h>