2016-04-01  Paul Eggert  <eggert@cs.ucla.edu>

    automake: port to Perl 5.22 and later

    Without this change, Perl 5.22 complains "Unescaped left brace in
    regex is deprecated" and this is planned to become a hard error in
    Perl 5.26.  See:
    http://search.cpan.org/dist/perl-5.22.0/pod/perldelta.pod#A_literal_%22{%22_should_now_be_escaped_in_a_pattern
    * bin/automake.in (substitute_ac_subst_variables): Escape left brace.