MINOR: htx/channel: Add a function to copy an HTX message in a channel's buffer

The channel_htx_copy_msg() function can now be used to copy an HTX message in a
channel's buffer. This function takes care to not overwrite existing data.

This patch depends on the commit "MINOR: htx: Add a function to append an HTX
message to another one". Both are mandatory to fix a bug in
http_reply_and_close() function. Be careful to backport both first.
1 file changed