At the same time, remove the "gen-certificate" target" since it is not
required as part of the build process and not documented elsewhere. This
script could be used for testing "examples/server".

fix ngtcp2.h: '@function' command should be used in a comment attache…

fix ngtcp2.h: '@function' command should be used in a comment attached to a function declaration [-Werror,-Wdocumentation]

travis: fix rpath

debug: num_bl(oc)ks is rename to ACK Block Count with draft-08