nodejs wrapper around libpd and portaudio

Tested on MAC OSX 10 and Raspbian Stretch Lite version 9 (raspberry pi 3) - for other platforms, dynamic libraries for libpd and portaudio should probably be built.

npm install [--save] node-libpd

# cf. test/index.js
$ npm run test

• pd.clear() to stop background processes
• find a proper way to organize tests
• allow to discover available devices and configuration for input and output => (maybe this should be done in a separate module)
• more generally expose more audio configuration options
• handle audio in
• implement array API
• refactor messaging struct (cf pd_msg_t)
  • use more specialized structs and dynamic_pointer_cast
  • use const and references as in PdReceiver callbacks
• re-enable addToSearchPath and clearSearchPath
• stop the whole pd and portaudio instances
• make init asynchronous to fix the race condition between js and worker threads (initialization can be quite long (> 100ms on mac OSX)). init should return a Promise => current workaround is to block the init method until currentTime != 0
• move LockedQueue implementation in .cpp file
• install babel thing to rewrite the index.js in es6
  • would be fancy to have an index.mjs and an index.js
• add a verbose options to init
• properly handle errors using : Nan::ThrowError("...");

libpd usage example (patch + test):

• https://github.com/libpd/libpd/tree/master/samples/cpp/pdtest

Node/Nan tutorial

• https://nodejs.org/api/addons.html#addons_wrapping_c_objects
• https://nodeaddons.com/book/
• https://medium.com/netscape/tutorial-building-native-c-modules-for-node-js-using-nan-part-1-755b07389c7c

libuv book:

• https://nikhilm.github.io/uvbook/threads.html

Debug with lldb:

• https://medium.com/@ccnokes/how-to-debug-native-node-addons-in-mac-osx-66f69f81afcb

TBD