Add HarfBuzz font backend for MS-Windows

Add HarfBuzz font backend for MS-Windows

* src/w32uniscribe.c [HAVE_HARFBUZZ]: Include math.h and
hb.h.
(bswap_32): Define for GCC 4.3.0 and later; else include
<byteswap.h> from Gnulib.
(struct uniscribe_font_info): Extend for HarfBuzz; 'cache' is
now a 'void *' (all users changed).
[HAVE_HARFBUZZ]: Define typedefs for HarfBuzz functions to be
loaded dynamically from the HarfBuzz DLL.  Define macros to
call those functions via function pointers.
(uniscribe_open) [HAVE_HARFBUZZ]: Use the HarfBuzz font driver
if the type of the font entity is 'harfbuzz'.
(uniscribe_close) [HAVE_HARFBUZZ]: For fonts using the
HarfBuzz backend, call hb_font_destroy to free memory used for
the cached hb_font data.
(uniscribe_shape): Fix assignment of character codepoints to
glyphs from a single cluster.
(w32hb_list, w32hb_match, free_cb, w32hb_get_font_table)
(w32hb_get_font, w32hb_encode_char, w32hb_begin_font)
(w32uni_combining, w32uni_general, w32uni_mirroring)
(get_hb_unicode_funcs, w32hb_shape)
(w32hb_combining_capability, load_harfbuzz_funcs)
[HAVE_HARFBUZZ]: New functions.
(syms_of_w32uniscribe_for_pdumper) [HAVE_HARFBUZZ]: Load the
HarfBuzz DLL and register the HarfBuzz backend with its
functions.
* src/w32font.c (syms_of_w32font) <Qharfbuzz>: New DEFSYM.
* src/w32fns.c (Fx_create_frame, w32_create_tip_frame)
[HAVE_HARFBUZZ]: Register the harfbuzz font backend.
* src/lisp.h (get_unicode_property): Declare prototype.
* src/font.h (harfbuzz_font_driver) [HAVE_NTGUI]: Declare.
* src/chartab.c (get_unicode_property): New function, body
taken from get-unicode-property-internal.
(Fget_unicode_property_internal): Call get_unicode_property
after validating input.

* doc/lispref/frames.texi (Font and Color Parameters):
* doc/emacs/msdos.texi (Windows Fonts): Document support for
HarfBuzz text shaping on MS-Windows.

* configure.ac (HAVE_HARFBUZZ): Move out of the X-specific
part, and consider HarfBuzz also for HAVE_W32 systems.
Require HarfBuzz v1.2.3 for w32.