QUIC: update stream flow control credit on STREAM_DATA_BLOCKED. Previously, after receiving STREAM_DATA_BLOCKED, current flow control limit was sent to client. Now, if the limit can be updated to the full window size, it is updated and the new value is sent to client, otherwise nothing is sent. The change lets client update flow control credit on demand. Also, it saves traffic by not sending MAX_STREAM_DATA with the same value twice.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


have=NGX_SUPPRESS_WARN . auto/have

have=NGX_SMP . auto/have