MINOR: h1: make h1_measure_trailers() take the byte count in argument

The principle is that it should not have to take this value from the
buffer itself anymore.
diff --git a/include/proto/h1.h b/include/proto/h1.h
index ada7d03..05d1877 100644
--- a/include/proto/h1.h
+++ b/include/proto/h1.h
@@ -43,7 +43,7 @@
 int h1_headers_to_hdr_list(char *start, const char *stop,
                            struct http_hdr *hdr, unsigned int hdr_num,
                            struct h1m *h1m);
-int h1_measure_trailers(const struct buffer *buf);
+int h1_measure_trailers(const struct buffer *buf, unsigned int max);
 
 #define H1_FLG_CTL  0x01
 #define H1_FLG_SEP  0x02