Fix compile error
Fix unit test
nghttp2_data_source_read_callback: Replace eof with uint32_t *data_flags

Replace int *eof with uint32_t *data_flags so that we can easily
extend functionality if we have to (but we don't do if possible).
Update tutorial
Announce h2-11
Name unnamed union in nghttp2_priority_spec so that we can be C90 compatible
nghttpx: Log when connection was upgraded to HTTP/2