MINOR: h1: Export some functions parsing the value of some HTTP headers

Functions parsing the value of "Connection:", "Transfer-encoding:" and
"Content-length:" headers are now exported to be used by the mux-h1.
diff --git a/include/proto/h1.h b/include/proto/h1.h
index 4914d51..a39cc0b 100644
--- a/include/proto/h1.h
+++ b/include/proto/h1.h
@@ -44,6 +44,10 @@
                            struct h1m *h1m, union h1_sl *slp);
 int h1_measure_trailers(const struct buffer *buf, unsigned int ofs, unsigned int max);
 
+int h1_parse_cont_len_header(struct h1m *h1m, struct ist *value);
+void h1_parse_xfer_enc_header(struct h1m *h1m, struct ist value);
+void h1_parse_connection_header(struct h1m *h1m, struct ist value);
+
 /* Macros used in the HTTP/1 parser, to check for the expected presence of
  * certain bytes (ef: LF) or to skip to next byte and yield in case of failure.
  */