Merge branch 'maint' (with fix for CVE-2012-3386)

Merge branch 'maint' (with fix for CVE-2012-3386)

This makes the fix for a locally-exploitable security vulnerability
(CVE-2012-3386) available to the Automake master branch.

* maint:
  sync: update files from upstream with "make fetch"
  news: improve wording in entry about CVE-2012-3386
  maint: post-release minor version bump
  release: stable release 1.12.2
  distcheck: never make part of $(distdir) world-writable
  compat: automake should substitute @mkdir_p@, for backward compatibility
  fixup: t/README: it's ./runtest, not ./t/ax/runtest

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>