JSSE: calling SSLSocket.close() should interrupt threads blocked in select()/poll()

[cconlon]

This PR adjusts JSSE and lower-level JNI behavior around SSLSocket.close(). When close() is called, it should interrupt any other threads blocked in select()/poll() from read()/write() operations.

This adds a pipe() descriptor which is watched by select()/poll(). That pipe is written to by a thread calling SSLSocket.close() to wake those blocked threads up - preventing a possible deadlock in this scenario.

This pipe() solution is currently only implemented for non-Windows platforms in this PR.

Should fix SunJSSE test: SSLSocketImpl/BlockedAsyncClose.java.

Minor fixes also included in this PR:

• Add ability to pass CFLAGS to java.sh, ie: CFLAGS="-DTEST_DEFINE" ./java.sh
• Add GitHub Action test for testing with -DWOLFJNI_USE_IO_SELECT defined (uses select() instead of poll())
• Update WolfSSLSocketTest TestServer/Client with CountDownLatch for proper Exception detection
• Fix Visual Studio warning about possible uninitialized pointer variable
• Remove incorrect ATOMIC_USER define gate around native wolfSSL_GetSide()