[Development] qt5 bundling harfbuzz

[Rex Dieter]

During review for qt5 packaging in fedora, we noticed qt5 includes a bundled 
copy of harfbuzz in src/3rdparty/harfbuzz/, and there currently doesn't seem 
to be --system-harfbuzz type build option available.

In order to justfify an exception to our usual "no bundled libraries" rule, 
I would need provide some answers to the following questions... so any 
help/input would be appreciated:

* Is the bundled library updated or is it (will be) one or more versions 
behind the latest upstream release?

* Is there any plan for unbundling the library at some later time?

* Has the library behaviour been modified? If so, 
** how has it been modified?
** why haven't the changes been pushed to the upstream library?


-- rex