DapInterface: shutdown sockets on Unix

FreeBSD could hang indefinitely when the debug-adapter process
terminated because we closed the TCP socket without first calling
`shutdown()`.  On that platform (and similarly on Linux and macOS)
a peer that is still blocked in `recv` will not be woken up unless
a full‐duplex shutdown is performed.

This patch adds `shutdown(fd, SHUT_RDWR)` in `DapInterface.cpp`
for Linux, *BSD, and macOS builds, preventing the observed hang.

source/dapinterface/DapInterface.cpp

@@ -258,9 +258,7 @@ namespace DAP
 			}
 			if (m_ServerSocket != -1)
 			{
-#if OS_LINUX
 				shutdown(m_ServerSocket, SHUT_RDWR);
-#endif
 				close(m_ServerSocket);
 				m_ServerSocket = -1;
 			}