[RELEASE] Released version 1.5.18

Released version 1.5.18 with the following main changes :
    - DOC: Clarify IPv4 address / mask notation rules
    - CLEANUP: fix inconsistency between fd->iocb, proto->accept and accept()
    - BUG/MEDIUM: fix maxaccept computation on per-process listeners
    - BUG/MINOR: listener: stop unbound listeners on startup
    - BUG/MINOR: fix maxaccept computation according to the frontend process range
    - MEDIUM: unblock signals on startup.
    - BUG/MEDIUM: channel: don't allow to overwrite the reserve until connected
    - BUG/MEDIUM: channel: incorrect polling condition may delay event delivery
    - BUG/MEDIUM: channel: fix miscalculation of available buffer space (3rd try)
    - MINOR: channel: add new function channel_congested()
    - BUG/MEDIUM: http: fix risk of CPU spikes with pipelined requests from dead client
    - BUG/MAJOR: channel: fix miscalculation of available buffer space (4th try)
    - BUG/MEDIUM: stream: ensure the SI_FL_DONT_WAKE flag is properly cleared
    - BUG/MEDIUM: channel: fix inconsistent handling of 4GB-1 transfers
    - MINOR: stats: fix typo in help messages
6 files changed