MINOR: proto_http: Externalisation of previously internal functions

Needs to expose the HTTP headers 'iterator' and the client's cookie
value extraction functions.
diff --git a/include/proto/proto_http.h b/include/proto/proto_http.h
index f5aef3b..0446b45 100644
--- a/include/proto/proto_http.h
+++ b/include/proto/proto_http.h
@@ -97,7 +97,11 @@
 int http_find_header2(const char *name, int len,
 		      char *sol, struct hdr_idx *idx,
 		      struct hdr_ctx *ctx);
+int http_find_next_header(char *sol, struct hdr_idx *idx,
+                          struct hdr_ctx *ctx);
 char *find_hdr_value_end(char *s, const char *e);
+char *extract_cookie_value(char *hdr, const char *hdr_end, char *cookie_name,
+                           size_t cookie_name_l, int list, char **value, int *value_l);
 int http_header_match2(const char *hdr, const char *end, const char *name, int len);
 int http_remove_header2(struct http_msg *msg, struct hdr_idx *idx, struct hdr_ctx *ctx);
 int http_header_add_tail2(struct http_msg *msg, struct hdr_idx *hdr_idx, const char *text, int len);