Bug 1475415 - Add first version of IPDL-JS API r=mrbkap,mccr8

Add the first version of the IPDL-JS API, which allow chrome JS to load IPDL files and use them to communicate accross Content processes.
See IPDLProtocol.h for more information regarding how to use the API.

Differential Revision: https://phabricator.services.mozilla.com/D2116

--HG--
rename : ipc/moz.build => ipc/ipdl_new/moz.build
extra : moz-landing-system : lando