Merge branch 'master' into ng/master

Merge branch 'master' into ng/master

* master: (21 commits)
  news: document deprecation of configure.in
  news: put planned backward compatibilities early
  sync: update files from upstream with "make fetch"
  maint: deprecate 'configure.in' as autoconf input
  maint: post-release minor version bump
  release: stable release 1.12.1
  copyright: update copyright years in a couple of files
  tests: avoid spurious failures with Solaris 9 cscope program
  maintcheck: fix a spurious failure
  perf: beginning of a performance testsuite
  aclocal: declare function prototypes, do not use '&' in function calls
  news: support for configure.in will be dropped in future automake versions
  missing: support AC_CONFIG_HEADERS in addition to obsolete AC_CONFIG_HEADER
  missing: don't bother checking for AM_CONFIG_HEADER: it is gone now
  docs: remove mention of AM_CONFIG_HEADER: it is obsolete and removed now
  tests: fix botched heading comments in 'lex-clean-cxx.sh'
  [ng] maintcheck: some tweaks and fixlets
  help: fix a typo in the list of warning categories
  maint: version bump after beta release
  release: beta release 1.12.0b (will become 1.12.1)
  ...

+ Extra non-trivial edits:

* Makefile.am (TESTS): Add the tests in the 't/perf' directory.

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