Update to 0.9.18.

Overview of changes leading to 0.9.18
Tuesday, May 28, 2013
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New build system:

- All unneeded code is all disabled by default,

- Uniscribe and CoreText shapers can be enabled with their --with options,

- icu_le and old shapers cannot be enabled for now,

- glib, freetype, and cairo will be detected automatically.
  They can be force on/off'ed with their --with options,

- icu and graphite2 are default off, can be enabled with their --with
  options,

Moreover, ICU support is now build into a separate library:
libharfbuzz-icu.so, and a new harfbuzz-icu.pc is shipped for it.
Distros can enable ICU now without every application on earth
getting linked to via libharfbuzz.so.

For distros I recommend that they make sure they are building --with-glib
--with-freetype --with-cairo, --with-icu, and optionally --with-graphite2;
And package harfbuzz and harfbuzz-icu separately.

(wiz)