role: new role ATK_ROLE_TITLE_BAR

https://bugzilla.gnome.org/show_bug.cgi?id=709351
role: new role ATK_ROLE_BLOCK_QUOTE

https://bugzilla.gnome.org/show_bug.cgi?id=710463
doc: Improve AtkObject::children-changed documentation

Specifically, adding the possibility to use NULL as the value for
the child if it is removed.

https://bugzilla.gnome.org/show_bug.cgi?id=684667
Merge branch 'master' of git://git.gnome.org/atk
JOHNE - Preliminary stuff for generating pkg-config files. Will probably get supplemented depending upon feedback from Todd