Update libp2p to v0.1.19

[kamilsa]

• I've followed this guide
  step by step carefully. [Yes|No]

• I've tested this package remotely and have excluded all broken builds.
  Here is the links to the Travis/AppVeyor with status "All passed":

  • https://ci.appveyor.com/project//hunter/build/
  • https://travis-ci.org//hunter/builds/

• I have submitted CI configs to https://github.com/cpp-pm/hunter-testing targeting pkg.template branch,
  see this merged pull request https://github.com/cpp-pm/hunter-testing/pull/

• My change will resolve this "New package" request: https://github.com/cpp-pm/hunter/issues/

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• I've followed this guide
  step by step carefully. [Yes|No]

• I've tested this package remotely and have excluded all broken builds.
  Here is the links to the Travis/AppVeyor with status "All passed":

  • https://ci.appveyor.com/project//hunter/build/
  • https://travis-ci.org//hunter/builds/

• This update will break few old toolchains.
  They are excluded in this pull request: https://github.com/cpp-pm/hunter-testing/pull/

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• I've checked this Git style guide. [Yes|No]
• I've checked this CMake style guide. [Yes|No]
• My change will work with CMake 3.2 (minimum requirement for Hunter). [Yes|No]
• I will try to keep this pull request as small as possible and will try not to mix unrelated features. [Yes|No]

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