[PATCH 4/5] imap-login: Add dict_reset side-channel command to imap-proxy
When imap_compress_on_proxy is enabled, DEFLATE compression runs inside
the imap-login process. The imap backend process cannot call
o_stream_deflate_reset_dict() directly on a remote stream, so this adds
a new side-channel command "dict_reset" that the backend can send to
trigger the dictionary reset on the proxy side.
Gbp-Pq: Name 0004-imap-login-Add-dict_reset-side-channel-command-to-im.patch