Since 5a468b38 we use SOL_LOCAL for the 2nd argument of getsockopt()
however Lion added the define SOL_LOCAL set to 0, which is the value to
the 2nd argument of getsockopt() for Unix sockets on Mac OS X. So
instead of using the define just pass 0 so we restore compatibility
with Snow Leopard and Leopard.

Reported at https://github.com/mxcl/homebrew/pull/23141