Increase the default buffer size for AF_UNIX from 8192 to 32768.

Increase the default buffer size for AF_UNIX from 8192 to 32768.

Using 8k for socketpairs was always on the low end side. Also this
avoid a fatal error in sshd that can be triggered when the network
stack is pushed hard enough to consume most of the allowed memory.
By increasing the default buffer size a bit the error in sshd is
avoided which is good enough for now.

Long term a better solution for sonewconn() and especially sbchecklowmem()
needs to be found. m_pool_used() returns not the right information for
them.

OK deraadt@ otto@