http2 update integration

https://github.com/warmcat/libwebsockets/issues/489

This

1) fixes the vhost changes on master

2) works around the ah pool changes

3) fixes some other build problems that appeared

4) hacks out physical flow control for internal streams

5) updates the advertised protocol to h2 needed by, eg, chrome 51

That gets it able to serve small (<4K, ie, one packet) files over http2

Signed-off-by: Andy Green <andy@warmcat.com>
diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index 0684326..cff8462 100644
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -392,6 +392,7 @@
 enum http_version {
 	HTTP_VERSION_1_0,
 	HTTP_VERSION_1_1,
+	HTTP_VERSION_2
 };
 
 enum http_connection_type {
@@ -1216,6 +1217,7 @@
 #endif
 
 	unsigned int hdr_parsing_completed:1;
+	unsigned int http2_substream:1;
 	unsigned int listener:1;
 	unsigned int user_space_externally_allocated:1;
 	unsigned int socket_is_permanently_unusable:1;
@@ -1562,7 +1564,7 @@
 
 #ifdef LWS_USE_HTTP2
 LWS_EXTERN void
-lws_context_init_http2_ssl(struct lws_context *context);
+lws_context_init_http2_ssl(struct lws_vhost *vhost);
 #else
 #define lws_context_init_http2_ssl(_a)
 #endif