* configure.ac: Use AC_CONFIG_HEADERS instead of AM_CONFIG_HEADER.
Use AC_USE_SYSTEM_EXTENSIONS instead of AC_GNU_SOURCE.
Use AS_HELP_STRING instead of AC_HELP_STRING.
(AC_TYPE_SIGNAL): Remove.
(AC_DECL_SYS_SIGLIST): Remove.
* m4/Makefile.am (EXTRA_DIST): Update.
* m4/gnupg-pth.m4: Remove.
* m4/onceonly.m4: Remove.
* m4/socklen.m4: Update from gnulib.
* m4/libtool.m4: Update from libgpg-error.
* m4/gpg-error.m4: Update from libgpg-error.