HTTP2: Update nghttp2 lib (0.6.7)

lot of change but it is majority reindent change (Using clang-format)

Change-Id: Idcd0fa79ca977e25d69eb80a89d3c61d228885e9
Reviewed-on: https://code.wireshark.org/review/5764
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>