The rewrite of BIND 9 build system is a large work and cannot be reasonable
split into separate merge requests.  Addition of the automake has a positive
effect on the readability and maintainability of the build system as it is more
declarative, it allows conditional and we are able to drop all of the custom
make code that BIND 9 developed over the years to overcome the deficiencies of
autoconf + custom Makefile.in files.

This squashed commit contains following changes:

- conversion (or rather fresh rewrite) of all Makefile.in files to Makefile.am
  by using automake

- the libtool is now properly integrated with automake (the way we used it
  was rather hackish as the only official way how to use libtool is via
  automake

- the dynamic module loading was rewritten from a custom patchwork to libtool's
  libltdl (which includes the patchwork to support module loading on different
  systems internally)

- conversion of the unit test executor from kyua to automake parallel driver

- conversion of the system test executor from custom make/shell to automake
  parallel driver

- The GSSAPI has been refactored, the custom SPNEGO on the basis that
  all major KRB5/GSSAPI (mit-krb5, heimdal and Windows) implementations
  support SPNEGO mechanism.

- The various defunct tests from bin/tests have been removed:
  bin/tests/optional and bin/tests/pkcs11

- The text files generated from the MD files have been removed, the
  MarkDown has been designed to be readable by both humans and computers

- The xsl header is now generated by a simple sed command instead of
  perl helper

- The <irs/platform.h> header has been removed

- cleanups of configure.ac script to make it more simpler, addition of multiple
  macros (there's still work to be done though)

- the tarball can now be prepared with `make dist`

- the system tests are partially able to run in oot build

Here's a list of unfinished work that needs to be completed in subsequent merge
requests:

- `make distcheck` doesn't yet work (because of system tests oot run is not yet
  finished)

- documentation is not yet built, there's a different merge request with docbook
  to sphinx-build rst conversion that needs to be rebased and adapted on top of
  the automake

- msvc build is non functional yet and we need to decide whether we will just
  cross-compile bind9 using mingw-w64 or fix the msvc build

- contributed dlz modules are not included neither in the autoconf nor automake