net: fix cgoAddrInfoFlags() on FreeBSD         CL 6250075 removed AI_MASK mask on all BSD variants,         however FreeBSD's AI_MASK does not include AI_V4MAPPED         and AI_ALL, and its libc is strict about the ai_flags.
net: fix cgoAddrInfoFlags() on FreeBSD
        CL 6250075 removed AI_MASK mask on all BSD variants,
        however FreeBSD's AI_MASK does not include AI_V4MAPPED
        and AI_ALL, and its libc is strict about the ai_flags.

        This will fix the FreeBSD builder.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/6305054

dsriram/golang,dsriram/golang,tv42/old-go,gnanderson/go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,tv42/old-go,tv42/old-go,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,apparentlymart/golang,apparentlymart/golang,gnanderson/go,gnanderson/go,dsriram/golang,tv42/old-go,gnanderson/go,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang