ACTION-1532: Investigate atk/at-spi mapping of role="text"

After much thought and discussion, what we will likely wind up doing is creating ATK_ROLE_STATIC (and ATSPI_ROLE_STATIC) for this and several other instances in which the role is known by the implementor but of no value to the user. The one mapping we definitely do not want is ATK_ROLE_TEXT.

https://bugzilla.gnome.org/show_bug.cgi?id=739981

Annnnnd, it's official.
1. There is a new ATK_ROLE_STATIC. Commit is here [1].
2. There is a new ATSPI_ROLE_STATIC. Commit is here [2].

Notes:

1. The docs on developer.gnome.org won't get updated until a new release of each module is done. That should happen next week.

2. The patches for the atk bridge [3] and pyatspi2 [4] will get committed after the 2.15.2 releases so the minimum version check makes sense. AFAIK, this doesn't impact implementation; it might impact regression tests depending on the testing harness of the implementor.

Transfering to Joseph as I believe my work here is done. :)

[1] https://git.gnome.org/browse/atk/commit/?id=c6e623b
[2] https://git.gnome.org/browse/at-spi2-core/commit/?id=9cbcd0a
[3] https://bugzilla.gnome.org/show_bug.cgi?id=740362
[4] https://bugzilla.gnome.org/show_bug.cgi?id=740364

Added ROLE_STATIC as stated to role mapping table for role="text":
http://rawgit.com/w3c/aria/master/core-aam/core-aam.html#role-map-text