build: Update to newer autoconf constructs.

* acinclude.m4 (GNUPG_CHECK_ENDIAN): Use AC_COMPILE_IFELSE instead of
AC_TRY_COMPILE.  Use AC_RUN_IFELSE instead of AC_TRY_RUN.
(GNUPG_BUILD_PROGRAM): Use AS_HELP_STRING instead of AC_HELP_STRING.
* configure.ac: Use AC_USE_SYSTEM_EXTENSIONS instead of AC_GNU_SOURCE.
Use AS_HELP_STRING instead of AC_HELP_STRING.
(AC_ISC_POSIX): Replace by AC_SEARCH_LIBS.
(AC_TYPE_SIGNAL): Remove.
* m4/isc-posix.m4: Remove.
* m4/codeset.m4: Update from gnulib.
* m4/gettext.m4: Update from gnulib.
* m4/lcmessage.m4: Update from gnulib.
* m4/socklen.m4: Update from gnulib.
* m4/ldap.m4: Use AS_HELP_STRING instead of AC_HELP_STRING.
Use AC_LINK_IFELSE instead of AC_TRY_LINK.
Use AC_RUN_IFELSE instead of AC_TRY_RUN.
* m4/gpg-error.m4: Update from libgpg-error.
* m4/readline.m4: Update from libgpg-error.
* m4/npth.m4: Update from npth.
* m4/libassuan.m4: Update from libassuan.
* m4/libgcrypt.m4: Update from libgcrypt.
* m4/ksba.m4: Update from libksba.
* m4/ntbtls.m4: Update from ntbtls.
* common/signal.c [!HAVE_DOSISH_SYSTEM] (init_one_signal): Replace
RETSIGTYPE to void.
[!HAVE_DOSISH_SYSTEM] (got_fatal_signal, got_usr_signal): Likewise.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

m4/socklen.m4

@@ -1,5 +1,5 @@
-# socklen.m4 serial 4
-dnl Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+# socklen.m4 serial 11
+dnl Copyright (C) 2005-2007, 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -8,45 +8,69 @@ dnl From Albert Chin, Windows fixes from Simon Josefsson.
 
 dnl Check for socklen_t: historically on BSD it is an int, and in
 dnl POSIX 1g it is a type of its own, but some platforms use different
-dnl types for the argument to getsockopt, getpeername, etc.  So we
-dnl have to test to find something that will work.
+dnl types for the argument to getsockopt, getpeername, etc.:
+dnl HP-UX 10.20, IRIX 6.5, OSF/1 4.0, Interix 3.5, BeOS.
+dnl So we have to test to find something that will work.
+
+AC_DEFUN([gl_TYPE_SOCKLEN_T],
+  [AC_REQUIRE([gl_CHECK_SOCKET_HEADERS])dnl
+   AC_CHECK_TYPE([socklen_t], ,
+     [AC_CACHE_CHECK([for socklen_t equivalent],
+        [gl_cv_socklen_t_equiv],
+        [# Systems have either "struct sockaddr *" or
+         # "void *" as the second argument to getpeername
+         gl_cv_socklen_t_equiv=
+         for arg2 in "struct sockaddr" void; do
+           for t in int size_t "unsigned int" "long int" "unsigned long int"; do
+             AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+                 [[#include <sys/types.h>
+                   #include <sys/socket.h>
+
+                   int getpeername (int, $arg2 *, $t *);]],
+                 [[$t len;
+                  getpeername (0, 0, &len);]])],
+               [gl_cv_socklen_t_equiv="$t"])
+             test "$gl_cv_socklen_t_equiv" != "" && break
+           done
+           test "$gl_cv_socklen_t_equiv" != "" && break
+         done
+         if test "$gl_cv_socklen_t_equiv" = ""; then
+           AC_MSG_ERROR([Cannot find a type to use in place of socklen_t])
+         fi
+        ])
+      AC_DEFINE_UNQUOTED([socklen_t], [$gl_cv_socklen_t_equiv],
+        [type to use in place of socklen_t if not defined])],
+     [gl_SOCKET_HEADERS])])
 
 dnl On mingw32, socklen_t is in ws2tcpip.h ('int'), so we try to find
-dnl it there first.  That file is included by gnulib's socket_.h, which
-dnl all users of this module should include.  Cygwin must not include
-dnl ws2tcpip.h.
-AC_DEFUN([gl_TYPE_SOCKLEN_T],
-  [AC_REQUIRE([gl_HEADER_SYS_SOCKET])dnl
-   AC_CHECK_TYPE([socklen_t], ,
-     [AC_MSG_CHECKING([for socklen_t equivalent])
-      AC_CACHE_VAL([gl_cv_gl_cv_socklen_t_equiv],
-	[# Systems have either "struct sockaddr *" or
-	 # "void *" as the second argument to getpeername
-	 gl_cv_socklen_t_equiv=
-	 for arg2 in "struct sockaddr" void; do
-	   for t in int size_t "unsigned int" "long int" "unsigned long int"; do
-	     AC_TRY_COMPILE(
-	       [#include <sys/types.h>
-		#include <sys/socket.h>
+dnl it there too.  But on Cygwin, wc2tcpip.h must not be included.  Users
+dnl of this module should use the same include pattern as gl_SOCKET_HEADERS.
+dnl When you change this macro, keep also in sync:
+dnl   - gl_CHECK_SOCKET_HEADERS,
+dnl   - the Include section of modules/socklen.
+AC_DEFUN([gl_SOCKET_HEADERS],
+[
+/* <sys/types.h> is not needed according to POSIX, but the
+   <sys/socket.h> in i386-unknown-freebsd4.10 and
+   powerpc-apple-darwin5.5 required it. */
+#include <sys/types.h>
+#if HAVE_SYS_SOCKET_H
+# include <sys/socket.h>
+#elif HAVE_WS2TCPIP_H
+# include <ws2tcpip.h>
+#endif
+])
 
-		int getpeername (int, $arg2 *, $t *);],
-	       [$t len;
-		getpeername (0, 0, &len);],
-	       [gl_cv_socklen_t_equiv="$t"])
-	     test "$gl_cv_socklen_t_equiv" != "" && break
-	   done
-	   test "$gl_cv_socklen_t_equiv" != "" && break
-	 done
-      ])
-      if test "$gl_cv_socklen_t_equiv" = ""; then
-	AC_MSG_ERROR([Cannot find a type to use in place of socklen_t])
-      fi
-      AC_MSG_RESULT([$gl_cv_socklen_t_equiv])
-      AC_DEFINE_UNQUOTED([socklen_t], [$gl_cv_socklen_t_equiv],
-	[type to use in place of socklen_t if not defined])],
-     [#include <sys/types.h>
-      #if HAVE_SYS_SOCKET_H
-      # include <sys/socket.h>
-      #elif HAVE_WS2TCPIP_H
-      # include <ws2tcpip.h>
-      #endif])])
+dnl Tests for the existence of the header for socket facilities.
+dnl Defines the C macros HAVE_SYS_SOCKET_H, HAVE_WS2TCPIP_H.
+dnl This macro must match gl_SOCKET_HEADERS.
+AC_DEFUN([gl_CHECK_SOCKET_HEADERS],
+  [AC_CHECK_HEADERS_ONCE([sys/socket.h])
+   if test $ac_cv_header_sys_socket_h = no; then
+     dnl We cannot use AC_CHECK_HEADERS_ONCE here, because that would make
+     dnl the check for those headers unconditional; yet cygwin reports
+     dnl that the headers are present but cannot be compiled (since on
+     dnl cygwin, all socket information should come from sys/socket.h).
+     AC_CHECK_HEADERS([ws2tcpip.h])
+   fi
+  ])