Add graphite smart font support

This was first reported on kde bug tracker (https://bugs.kde.org/show_bug.cgi?id=251665), but was closed as "UPSTREAM" and I was suggested to report it here, so here I am...

Graphite is an amazing smart font technology developed by SIL.
Copy/pasting from wikipedia:

"Graphite is based on the TrueType font format, and adds three of its own
tables. It allows for all kinds of smart rendering rules, including ligatures,
glyph substitution, glyph insertion, glyph rearrangement, anchoring diacritics,
kerning, and justification. Graphite rules may be sensitive to the context. For
instance, there might be a glyph substitution rule that replaces every
non-final s by an ſ.
In a Graphite font, all smart rendering information resides within the font
file. In order to display the Graphite smart rendering, an application needs
only Graphite support, but no built-in knowledge about the writing system's
rendering. This makes Graphite especially suited for minority writing systems
that cannot rely on applications to provide built-in rendering information. In
this regard, Graphite is similar to AAT, but different from OpenType which
requires applications to provide built-in rendering information."

I'm using it on OOo Writer and must say it is awesome: REAL sub/superscripts,
REAL small caps, ligatures... everything just appending a proper "tag" to the
font name.
And I'm using a western language (mainly Spanish and Italian): for other
languages Graphite is almost a must.
To understand how it works, just try Magyar Linux Libertine font on Writer,
enable "tex mode" by adding :214=1 to the font name:

Magyar Linux Libertine G:214=1

and type something like SO_4^2^-
As far as I understand it (which is little), graphite support on OOo comes
through pango-graphite library, which is gtk based... It would be great to
have this also on qt apps.

So the "wish" is: Give to Qt the ability to use graphite substitution tables, either by graphical menu or by
using "extended font names" as OOo do.

LINKS:
Graphite on wikipedia:
http://en.wikipedia.org/wiki/Graphite_(SIL)
Graphite on SIL website:
http://scripts.sil.org/cms/scripts/page.php?&cat_id=RenderingGraphite
Magyar Linux Libertine font:
http://numbertext.org/linux/