config/
* override.m4: Use m4_version_prereq throughout.
(_AC_ARG_VAR_VALIDATE, AC_MSG_FAILURE): Backport from git
Autoconf: output pwd along with fatal errors, so the right
config.log file is hinted at more prominently.
(PARSE_ARGS): Push setting of ac_pwd in this diversion.
(_GCC_AUTOCONF_VERSION): New, define to 2.59 if not defined.
(_GCC_AUTOCONF_VERSION_CHECK): New macro, require use of Autoconf
version _GCC_AUTOCONF_VERSION throughout the tree.
(m4_wrap): New override, fix for Posix semantics of m4wrap.