Use Tor Browser's integrated `AF_LOCAL` support on alpha.

The tbb_stub.so used by sandboxed-tor-browser currently overloads socket() and connect() to force Firefox into using an AF_LOCAL socket for the control and socks ports.

Once the stable release series has first class support for AF_LOCAL, the surrogate and stub should be changed to use those over the hack to reduce the amount of code in the stub.

Note: The stub has other duties and likely will be impossible to eliminate entirely, but the smaller the stub is the better.