https://github.com/harfbuzz/harfbuzz/issues/1652

Let's see if I can make a release on Mac...

This adds support to the CMake build files to support building
HarfBuzz-GObject, which is actually a little bit complicated,
as we need to:

-Run glib-mkenums, which is a Python (for newer GLib/GObject) or PERL
 (for older, pre 2.53.4, GLib/GObject) script.  This matters more for
 Visual Studio builds as shebang lines are not supported, so we need to
 test-run it with PERL or Python to determine which is the correct
 interpretor to use.

-Next, we need to replace strings in the sources that we obtain from
 running glib-mkenums.  So, the solution here is to use a small utility
 CMake script for our purposes here, to maintain maximum compatibility.

-Ensure that things do work in the Visual Studio IDE builds.

Android uses its own file these days and third-party developers should
be using the autotools-based system against Android NDK.

This adds a set of NMake Makefiles that can be used to build HarfBuzz, from
the standard basic build building the minimal HarfBuzz DLL (consisting
of OpenType, fallback and Uniscribe support only), to a full fledged build
consisting of GLib and FreeType support, as well as building the utilities,
the test programs in src/ and test/api, and HarfBuzz-ICU and
HarfBuzz-GObject, and up to building the introspection files.  This means a
flexible build mechanism is supported here, so anything that is supported
for a Windows build (code-wise), should all be supported by this build
system.

As in an earlier commit, the source listings are shared with the autotools
builds with the various Makefile.sources in src/, src/hb-ucdn and util/, and
this set of NMake Makefiles will transform these lists into the form they
want.

In the current form, all the test programs in test/api pass, and this has
been checked successfully with 'make -j8 distcheck'.

Initial setup of gtk-doc. Straight forward setup following the gtk-doc
instructions. Ignore some troublesome types in src/hb-gobject.h. To
build use "./autogen.sh --enable-gtk-doc" then "make". Docs are in
harfbuzz/docs/reference/html/index.html.

Currently it only works with ICU that has .pc files.  I'll
wait till someone complains before fixing it for icu-config
systems.

    Move reusable list of files into variable definitions modules can
    reuse

This reverts commit 01013a0f.

Conflicts:
	config.h.in

Same argument as previous commit.

I typically don't like including generating files in tree.  But like to
make an exception for this, since this forms the canonical list of
options one would need to go through when building with alternative
build systems.

A *real* release this time, with NEWS, ChangeLog, etc.

Adds check-valgrind among other modes.  We do not run under gtester by
default anymore.

Uses the glib testing framework.  Wrote unit tests for hb-common.h
types.