MEDIUM: compression: Adapt to be compatible with the HTX representation

MEDIUM: compression: Adapt to be compatible with the HTX representation

Functions analyzing request and response headers have been duplicated and
adapted to support HTX messages. The callback http_payload have been implemented
to handle the data compression itself. It loops on HTX blocks and replace
uncompressed value of DATA block by compressed one. Unlike the HTTP legacy
version, there is no chunk at all. So HTX version is significantly easier.