Add an unpatched version of xz, XZ Utils, to /trunk/deps/third_party

xz/src/xz/signals.h

+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       signals.h
+/// \brief      Handling signals to abort operation
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+/// If this is true, we will clean up the possibly incomplete output file,
+/// return to main() as soon as practical. That is, the code needs to poll
+/// this variable in various places.
+extern volatile sig_atomic_t user_abort;
+
+
+/// Initialize the signal handler, which will set user_abort to true when
+/// user e.g. presses C-c.
+extern void signals_init(void);
+
+
+#if (defined(_WIN32) && !defined(__CYGWIN__)) || defined(__VMS)
+#       define signals_block() do { } while (0)
+#       define signals_unblock() do { } while (0)
+#else
+/// Block the signals which don't have SA_RESTART and which would just set
+/// user_abort to true. This is handy when we don't want to handle EINTR
+/// and don't want SA_RESTART either.
+extern void signals_block(void);
+
+/// Unblock the signals blocked by signals_block().
+extern void signals_unblock(void);
+#endif
+
+#if defined(_WIN32) && !defined(__CYGWIN__)
+#       define signals_exit() do { } while (0)
+#else
+/// If user has sent us a signal earlier to terminate the process,
+/// re-raise that signal to actually terminate the process.
+extern void signals_exit(void);
+#endif