Refs #100864 Restructure CCN plugin for VLC to work reliably on Android

Remove FIFO connecting CCN and Input threads, and related preferences.
Add boolean preference "ccn-tcp-connect" (default: true) to control whether
    the plugin explicitly connects to the local ccnd via TCP or honors the
    environment variables (which default to using Unix domain socket).
Add counter for failed content object requests, display in log on stream close.
Restructure code to use blocking gets for requested data but an asynchronous
    thread for processing prefetch responses, and separate CCN handles for
    data an prefetch.
Improve storage allocation/deallocation behavior.

Author: Nick Briggs