[REORG] http: move HTTP error codes back to proto_http.h

This one was left isolated in its own file. It probably is a leftover
from the 1.2->1.3 split.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 214cdf5..e9532ed 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -41,9 +41,9 @@
 #include <types/buffers.h>
 #include <types/counters.h>
 #include <types/freq_ctr.h>
-#include <types/httperr.h>
 #include <types/log.h>
 #include <types/protocols.h>
+#include <types/proto_http.h>
 #include <types/session.h>
 #include <types/server.h>
 #include <types/stick_table.h>