Travis test

server (example): fix typo on function name

work with autotools and cmake

generate_reserved_vesrion => generate_reserved_version

This also commit adds ngtcp2_pkt_write_version_negotiation, and
deprecates ngtcp2_upe_encode_version_negotiation.  This commit fixes
the issue that server does not send random value in Unused field of
Version Negotiation packet.

cmake: add also remove -Wno-noexcept-type for cmake

Add Wduplicated-branches (gcc7) CFLAGS

Simplify test certificate creation

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