[RELEASE] Released version 1.5.1

Released version 1.5.1 with the following main changes :
    - BUG/MINOR: config: http-request replace-header arg typo
    - BUG/MINOR: ssl: rejects OCSP response without nextupdate.
    - BUG/MEDIUM: ssl: Fix to not serve expired OCSP responses.
    - BUG/MINOR: ssl: Fix OCSP resp update fails with the same certificate configured twice.     (cherry picked from commit 1d3865b096b43b9a6d6a564ffb424ffa6f1ef79f)
    - BUG/MEDIUM: Consistently use 'check' in process_chk
    - BUG/MAJOR: session: revert all the crappy client-side timeout changes
    - BUG/MINOR: logs: properly initialize and count log sockets
6 files changed