* Makefile.am: Add variables languages, dist_languages,
distcheck_languages, release_languages, sign_release_languages,
distclean_languages. Add rules for nested language bindings.
(distclean-local, dist-all, distcheck-all, release-all,
sign-release-all): New rules.
(.PHONY): Add all new rules.
* autogen-all.sh: New.
* configure.ac: Add cpp to available languages if subdir exists. Add
cpp to nested languages if enabled to generate corresponding make
targets. Call configure script of nested cpp package recursively.
* lang/cpp/configure.ac: Check if gpgmepp is built as nested package
and set GPGME_CFLAGS and GPGME_LIBS accordingly.
--
This re-adds the ability to build the C++ bindings together with gpgme
with a single `configure && make` command (if building from git). It
also adds make targets for running dist, distcheck, release and
sign-release for gpgme and all enabled nested languages with a single
make command.
GnuPG-bug-id: 7110
