[portaudio] c++ binding not installed

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**Is your feature request related to a problem? Please describe.**

PortAudio comes with a cxx binding in its source under[ "bindings/cpp"](https://app.assembla.com/spaces/portaudio/git/source/master/bindings/cpp) as noted by [its website](http://www.portaudio.com/links.html). However, vcpkg does not install or build it as a part of the installation of the port (I didn't find any related headers in vcpkg\installed\x64-windows\include), so the user cannot conveniently use this official binding.

**Proposed solution**

Install this binding as a part of portaudio.

**Describe alternatives you've considered**

This binding itself has a cmake build file so maybe we can add another port which depends on the current one.

**Additional context**

N/A.