In java-nio.cpp, we can't use GetPrimitiveArrayCritical when reading
from or writing to blocking sockets since it may block the rest of the
VM indefinitely.
In SelectableChannel.java, we can't use a null test on
SelectableChannel.key to determine whether the channel is open since
it might never be registered with a Selector. According to the Sun
documentation, a SelectableChannel is open as soon as it's created, so
that's what we now implement.
On POSIX systems, Avian sends a special signal to a thread to
implement Thread.getStackTrace() when called from a different thread.
If the target thread is blocked on a call to accept when this happens,
it will return -1, with errno set to EINTR. Instead of treating this
as an error, we now just loop and call accept again.
and server socket channels are implemented. This version works but only when
libnative is linked with g++ (because of C++ object creation code that fails
without this linking)
