attempt to avoid race condition when initializing list of async signals * cxx-signal-helpers.cc: New file. Move (async_signals): New file-scope static const variable. (octave_block_async_signals, octave_unblock_async_signals, signal_watcher, octave_create_interrupt_watcher_thread): Move functions here from signal-wrappers.c. Use file-scope async_signals variable instead of calling octave_async_signals to get list of asynchronous signals. (init_async_signals): Rename from octave_async_signals and move here from signal-wrappers.cc. Return sigset_t object instead of pointer to static storage that is local to the function. * module.mk: Update.

--- a/liboctave/wrappers/module.mk	Sun Jan 29 13:03:23 2023 -0500
+++ b/liboctave/wrappers/module.mk	Thu Dec 08 13:57:18 2022 -0500
@@ -46,6 +46,7 @@
   %reldir%/async-system-wrapper.c \
   %reldir%/base64-wrappers.c \
   %reldir%/canonicalize-file-name-wrapper.c \
+  %reldir%/cxx-signal-helpers.cc \
   %reldir%/dirent-wrappers.c \
   %reldir%/fcntl-wrappers.c \
   %reldir%/filepos-wrappers.c \