Move to gawk-3.1.7.

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diff --git a/libsigsegv/m4/sigaltstack-longjmp.m4 b/libsigsegv/m4/sigaltstack-longjmp.m4
new file mode 100644
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+++ b/libsigsegv/m4/sigaltstack-longjmp.m4
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+# sigaltstack-longjmp.m4 serial 6 (libsigsegv-2.7)
+dnl Copyright (C) 2002-2003, 2006, 2008 Bruno Haible <bruno@clisp.org>
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+dnl How to longjmp out of a signal handler, in such a way that the
+dnl alternate signal stack remains functional.
+dnl SV_TRY_LEAVE_HANDLER_LONGJMP(KIND, CACHESYMBOL, KNOWN-SYSTEMS,
+dnl                              INCLUDES, RESETCODE)
+AC_DEFUN([SV_TRY_LEAVE_HANDLER_LONGJMP],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  AC_CACHE_CHECK([whether a signal handler can be left through longjmp$1], [$2], [
+    AC_RUN_IFELSE([
+      AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <signal.h>
+#include <setjmp.h>
+$4
+#if HAVE_SETRLIMIT
+# include <sys/types.h>
+# include <sys/time.h>
+# include <sys/resource.h>
+#endif
+#ifndef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
+jmp_buf mainloop;
+sigset_t mainsigset;
+int pass = 0;
+void stackoverflow_handler (int sig)
+{
+  pass++;
+  sigprocmask (SIG_SETMASK, &mainsigset, NULL);
+  { $5 }
+  longjmp (mainloop, pass);
+}
+volatile int * recurse_1 (volatile int n, volatile int *p)
+{
+  if (n >= 0)
+    *recurse_1 (n + 1, p) += n;
+  return p;
+}
+int recurse (volatile int n)
+{
+  int sum = 0;
+  return *recurse_1 (n, &sum);
+}
+int main ()
+{
+  char mystack[2 * SIGSTKSZ];
+  stack_t altstack;
+  struct sigaction action;
+  sigset_t emptyset;
+#if defined HAVE_SETRLIMIT && defined RLIMIT_STACK
+  /* Before starting the endless recursion, try to be friendly to the user's
+     machine.  On some Linux 2.2.x systems, there is no stack limit for user
+     processes at all.  We don't want to kill such systems.  */
+  struct rlimit rl;
+  rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
+  setrlimit (RLIMIT_STACK, &rl);
+#endif
+  /* Install the alternate stack.  Use the midpoint of mystack, to guard
+     against a buggy interpretation of ss_sp on IRIX.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
+  altstack.ss_flags = 0; /* no SS_DISABLE */
+  if (sigaltstack (&altstack, NULL) < 0)
+    exit (1);
+  /* Install the SIGSEGV handler.  */
+  sigemptyset (&action.sa_mask);
+  action.sa_handler = &stackoverflow_handler;
+  action.sa_flags = SA_ONSTACK;
+  sigaction (SIGSEGV, &action, (struct sigaction *) NULL);
+  sigaction (SIGBUS, &action, (struct sigaction *) NULL);
+  /* Save the current signal mask.  */
+  sigemptyset (&emptyset);
+  sigprocmask (SIG_BLOCK, &emptyset, &mainsigset);
+  /* Provoke two stack overflows in a row.  */
+  if (setjmp (mainloop) < 2)
+    {
+      recurse (0);
+      exit (2);
+    }
+  exit (0);
+}]])],
+      [$2=yes],
+      [$2=no],
+      [case "$host" in
+         m4_if([$3], [], [], [[$3]) $2=yes ;;])
+         *) $2="guessing no" ;;
+       esac
+      ])
+  ])
+])