remove special sigint handling for Windows systems * sighandlers.cc (sigint_handler, (octave_catch_interrupts): Delete special case for Windows. (w32_sigint_handler): Delete function. * sysdep.cc (MINGW_signal_cleanup): Don't call w32_raise_final. (MINGW_initMSVC_init): Don't call w32_sigint_init or w32_set_quiet_shutdown. * sysdep.h: Don't define USE_W32_SIGINT. * cquit.c (PRINT_CURRENT_THREAD, DEBUGs, DEBUGd): Delete macros. (w32_thread_setjmp_mutex, w32_signal_context, w32_signal_to_raise, w32_main_thread_id, w32_main_thread, w32_restore_thread): Delete global and static variables. (w32_in_main_thread, w32_reset_context, w32_raise_in_main, w32_raise_final, w32_raise, w32_sigint_init): Delete functions.