A null handler for the signal used to interrupt blocking operations.
The null signal handler for the interrupt signal is called from a static initialization block of
NativeThread. I need to set up the signal handler at runtime. The null signal
handler is also set up, at runtime, when libjvm is loaded, from the
init() methods
of /jdk8u-dev/jdk/src/solaris/native/java/net/bsd_close.c, and
/jdk8u-dev/jdk/src/solaris/native/java/net/linux_close.c. I consolidate all the calls in an
PosixInterruptSignalUtils.ensureInitialized() method that is called at runtime by the various users.
Adapted from /jdk8u-dev/jdk/src/solaris/native/sun/nio/ch/NativeThread.c, but shared by anyone
who sends C signals to interrupt blocked operations.