Update libcurl from 7.54.1 to 7.55.1.

Bug: http://b/64610131
Test: builds, boots, `vendor/google/tools/fake-ota on streaming` works
Change-Id: I7ecaf9c83e9496ac4a379507791bec637deaa4cb
diff --git a/lib/http2.h b/lib/http2.h
index 8917535..f597c80 100644
--- a/lib/http2.h
+++ b/lib/http2.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -53,6 +53,12 @@
 void Curl_http2_setup_req(struct Curl_easy *data);
 void Curl_http2_done(struct connectdata *conn, bool premature);
 CURLcode Curl_http2_done_sending(struct connectdata *conn);
+CURLcode Curl_http2_add_child(struct Curl_easy *parent,
+                              struct Curl_easy *child,
+                              bool exclusive);
+void Curl_http2_remove_child(struct Curl_easy *parent,
+                             struct Curl_easy *child);
+void Curl_http2_cleanup_dependencies(struct Curl_easy *data);
 #else /* USE_NGHTTP2 */
 #define Curl_http2_init(x) CURLE_UNSUPPORTED_PROTOCOL
 #define Curl_http2_send_request(x) CURLE_UNSUPPORTED_PROTOCOL
@@ -65,6 +71,9 @@
 #define Curl_http2_init_userset(x)
 #define Curl_http2_done(x,y)
 #define Curl_http2_done_sending(x)
+#define Curl_http2_add_child(x, y, z)
+#define Curl_http2_remove_child(x, y)
+#define Curl_http2_cleanup_dependencies(x)
 #endif
 
 #endif /* HEADER_CURL_HTTP2_H */