compat: automake should substitute @mkdir_p@, for backward compatibility That has been unwittingly broken by commit v1.12-19-g7a1eb9f of 2012-04-28, "AM_PROG_MKDIR_P: deprecate, to be removed in Automake 1.13". We thought it wasn't a big deal, but Jim Meyering reported that @mkdir_p@ is used in gettext's Makefile.in.in template: <http://lists.gnu.org/archive/html/automake/2012-07/msg00014.html> * lib/am/header-vars.am (mkdir_p): Don't define. * m4/init.m4 (AM_INIT_AUTOMAKE): AC_SUBST 'mkdir_p' with $(MKDIR_P). * t/mkdir_p.sh, t/mkdirp-deprecation.sh: Enhance. * NEWS: Update. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>