REORG: h1: move legacy http functions to http_msg.c

Now that h1 and legacy HTTP are two distinct things, there's no need
to keep the legacy HTTP parsers in h1.c since they're only used by
the legacy code in proto_http.c, and h1.h doesn't need to include
hdr_idx anymore. This concerns the following functions :

- http_parse_reqline();
- http_parse_stsline();
- http_msg_analyzer();
- http_forward_trailers();

All of these were moved to http_msg.c.
diff --git a/include/proto/proto_http.h b/include/proto/proto_http.h
index c32a555..329e641 100644
--- a/include/proto/proto_http.h
+++ b/include/proto/proto_http.h
@@ -51,6 +51,13 @@
 void http_msg_analyzer(struct http_msg *msg, struct hdr_idx *idx);
 void http_txn_reset_req(struct http_txn *txn);
 void http_txn_reset_res(struct http_txn *txn);
+const char *http_parse_reqline(struct http_msg *msg,
+                               enum h1_state state, const char *ptr, const char *end,
+                               unsigned int *ret_ptr, enum h1_state *ret_state);
+const char *http_parse_stsline(struct http_msg *msg,
+                               enum h1_state state, const char *ptr, const char *end,
+                               unsigned int *ret_ptr, enum h1_state *ret_state);
+int http_forward_trailers(struct http_msg *msg);
 int http_legacy_replace_header(struct hdr_idx *idx, struct http_msg *msg,
                                const char *name, unsigned int name_len,
                                const char *str, struct my_regex *re,