Adds modified libjingle.gyp for faster builds

We maintain our own modified version of libjingle.gyp build file. This removes dependency on NSS, media/Webrtc portions of the code. It would be smarter to simply store a diff but this is more dummy-proof. Perhaps in the future, ipop-tincan will have its own independent gyp build that links to libjingle instead of current method. But this is not a priority at the moment.